addition Stripe payment integration work

Feat discrete accounts

README.md

@@ -1,9 +1,9 @@
 # Koin Ping
+A lightweight on-chain monitoring and alerting system designed to give users situational awareness over blockchain addresses they care about.
 
-Koin Ping is an MIT-licensed blockchain monitoring system by Steven Jannette
-that polls Ethereum addresses for on-chain activity and delivers real-time
-alerts to users via a Go REST API backend and a React single-page application
-frontend.
+# Overview
+
+Koin Ping observes on-chain activity and notifies users when predefined conditions are met. It does not execute transactions, manage wallets, or speculate on prices.
 
 ## Getting Started
 
@@ -45,16 +45,16 @@ cd frontend && npm run dev
 ```
 
 The API listens on `http://localhost:3001` and the frontend on
-`http://localhost:3000` by default.
+`http://localhost:3000` by default for development.
 
 ## Rationale
 
-Crypto users who hold or actively monitor addresses need a lightweight, reliable
-way to know when on-chain activity occurs without polling block explorers
-manually. Koin Ping fills that gap: it watches a set of Ethereum addresses,
-evaluates configurable alert rules (incoming transactions, outgoing
-transactions, large transfers, balance thresholds), and notifies the user
-through Discord webhooks.
+Crypto users may actively monitor addresses with webhooks integrating popular 
+messaging platforms: Discord, Slack, Telegram.
+This lightweight, reliable framework makes instant awareness of on-chain 
+activity trivial, without polling block explorers manually. Koin Ping watches 
+addresses, evaluates configurable alert rules (incoming transactions, outgoing 
+transactions, "large" transfers, balance thresholds), and sends notifications.
 
 ## Design
 
@@ -99,6 +99,52 @@ to the database, and dispatches Discord notifications.
 Firebase, communicates with the API via fetch, and renders the address/alert
 management UI.
 
+## Setting Up Your Alert Platforms
+
+Koin Ping can send real-time alerts to **Telegram**, **Discord**, **Slack**, and **Email**. Each channel is configured per-user through the **Notification Settings** panel on the Alerts page.
+
+Below are step-by-step guides for setting up each platform.
+
+---
+
+### Telegram
+
+To receive alerts via Telegram, you need to create a bot and get your chat ID.
+
+#### 1. Create a Telegram Bot
+
+1. Open Telegram and search for **@BotFather** (look for the blue verified checkmark).
+2. Open the conversation with BotFather and send: `/newbot`
+3. BotFather will ask for a **display name** — enter something like `Koin Ping Alerts`.
+4. BotFather will ask for a **username** — it must end in `bot`, e.g. `MyKoinPingBot`.
+5. BotFather will reply with your **Bot Token** — a string that looks like `123456789:ABCdefGHIjklMNOpqrSTUvwxYZ`. Copy it.
+
+#### 2. Get Your Chat ID
+
+1. In Telegram, search for the bot username you just created and open the chat.
+2. Tap **Start** or send any message (e.g. `hello`).
+3. Open the following URL in your browser, replacing `YOUR_BOT_TOKEN` with the token from step 1:
+
+   ```
+   https://api.telegram.org/botYOUR_BOT_TOKEN/getUpdates
+   ```
+
+4. In the JSON response, find the `"chat"` object — the `"id"` field is your **Chat ID** (a numeric value).
+
+   > **Tip:** If the `'result"` array is empty, make sure you sent a message to your bot first, then refresh the page.
+
+#### 3. Save in Koin Ping
+
+1. Go to the **Alerts** page in Koin Ping.
+2. In the **Notification Settings** panel, find the **Telegram** section.
+3. Paste your **Bot Token** and **Chat ID** into the corresponding fields.
+4. Click **Save Settings**.
+5. Click **Test All Channels** to verify — you should receive a test message from your bot in Telegram.
+
+---
+
+*Guides for Discord, Slack, and Email coming soon.*
+
 ## License
 
 MIT. See [LICENSE](LICENSE).
@@ -106,3 +152,5 @@ MIT. See [LICENSE](LICENSE).
 ## Author
 
 Steven Jannette
+
+

backend-go/README.md

@@ -2,6 +2,19 @@ Start DB:
 
 brew services start postgresql@15
 
-Run Backend:
+From the backend-go directory, you have a few options:
 
-cd /Users/kjannette/workspace/koin_ping/backend-go go run ./cmd/api
+Option 1: Single command (both API + poller)
+cd /Users/kjannette/workspace/koin_ping_0.2.0/backend-gomake dev-all
+
+Option 2: Two separate terminals
+Terminal 1 (API server):
+cd /Users/kjannette/workspace/koin_ping_0.2.0/backend-go go run ./cmd/api
+Terminal 2 (Poller):
+cd /Users/kjannette/workspace/koin_ping_0.2.0/backend-go go run ./cmd/poller
+
+make run — Builds and runs the API server.
+make dev — Runs the API server with auto-reload via air (falls back to go run if air isn't installed).
+make poller — Builds and runs the poller.
+make poller-dev — Runs the poller with auto-reload.
+make dev-all — Runs both the API and poller concurrently.

backend-go/cmd/api/main.go

@@ -44,9 +44,11 @@ func main() {
 
 	defer database.Close()
 
+	userModel := models.NewUserModel(pool)
 	addressModel := models.NewAddressModel(pool)
 	alertRuleModel := models.NewAlertRuleModel(pool)
 	alertEventModel := models.NewAlertEventModel(pool)
+	checkpointModel := models.NewCheckpointModel(pool)
 	notifConfigModel := models.NewNotificationConfigModel(pool)
 
 	emailDigestSvc := services.NewEmailDigestService(
@@ -58,51 +60,72 @@ func main() {
 	alertEventHandler := handlers.NewAlertEventHandler(alertEventModel)
 	notifConfigHandler := handlers.NewNotificationConfigHandler(notifConfigModel, cfg)
 	emailDigestHandler := handlers.NewEmailDigestHandler(emailDigestSvc, notifConfigModel)
+	statusHandler := handlers.NewStatusHandler(checkpointModel)
+	stripeHandler := handlers.NewStripeHandler(userModel, cfg)
+
+	authenticate := middleware.Authenticate(userModel)
+	requireSub := middleware.RequireSubscription(userModel)
+
+	// authAndSub chains authentication + subscription check for protected routes.
+	authAndSub := func(h http.Handler) http.Handler {
+		return authenticate(requireSub(h))
+	}
 
 	mux := http.NewServeMux()
 	b := cfg.APIBasePath // e.g. "/v1"
 
 	// Public routes
 	mux.HandleFunc("GET "+b+"/health", handlers.HealthCheck)
-	mux.HandleFunc("GET "+b+"/status", handlers.SystemStatus)
+	mux.HandleFunc("GET "+b+"/status", statusHandler.GetStatus)
 
-	// Authenticated routes — addresses
+	// Stripe webhook (public — called by Stripe, not authenticated)
+	mux.HandleFunc("POST "+b+"/stripe/webhook", stripeHandler.HandleWebhook)
+
+	// Stripe routes (auth required, NO subscription required)
+	mux.Handle("POST "+b+"/stripe/create-checkout-session",
+		authenticate(http.HandlerFunc(stripeHandler.CreateCheckoutSession)))
+	mux.Handle("GET "+b+"/stripe/subscription-status",
+		authenticate(http.HandlerFunc(stripeHandler.GetSubscriptionStatus)))
+
+	// Authenticated + subscribed routes — addresses
 	mux.Handle("POST "+b+"/addresses",
-		middleware.Authenticate(http.HandlerFunc(addressHandler.Create)))
+		authAndSub(http.HandlerFunc(addressHandler.Create)))
 	mux.Handle("GET "+b+"/addresses",
-		middleware.Authenticate(http.HandlerFunc(addressHandler.List)))
+		authAndSub(http.HandlerFunc(addressHandler.List)))
 	mux.Handle("DELETE "+b+"/addresses/{addressId}",
-		middleware.Authenticate(http.HandlerFunc(addressHandler.Remove)))
+		authAndSub(http.HandlerFunc(addressHandler.Remove)))
+	mux.Handle("PATCH "+b+"/addresses/{addressId}",
+		authAndSub(http.HandlerFunc(addressHandler.UpdateLabel)))
 
-	// Authenticated routes for alert rules
+	// Authenticated + subscribed routes — alert rules
 	mux.Handle("POST "+b+"/addresses/{addressId}/alerts",
-		middleware.Authenticate(http.HandlerFunc(alertRuleHandler.Create)))
+		authAndSub(http.HandlerFunc(alertRuleHandler.Create)))
 	mux.Handle("GET "+b+"/addresses/{addressId}/alerts",
-		middleware.Authenticate(http.HandlerFunc(alertRuleHandler.ListByAddress)))
+		authAndSub(http.HandlerFunc(alertRuleHandler.ListByAddress)))
 	mux.Handle("PATCH "+b+"/alerts/{alertId}",
-		middleware.Authenticate(http.HandlerFunc(alertRuleHandler.UpdateStatus)))
+		authAndSub(http.HandlerFunc(alertRuleHandler.UpdateStatus)))
 	mux.Handle("DELETE "+b+"/alerts/{alertId}",
-		middleware.Authenticate(http.HandlerFunc(alertRuleHandler.Remove)))
+		authAndSub(http.HandlerFunc(alertRuleHandler.Remove)))
 
-	// Authenticated routes — alert events
+	// Authenticated + subscribed routes — alert events
 	mux.Handle("GET "+b+"/alert-events",
-		middleware.Authenticate(http.HandlerFunc(alertEventHandler.List)))
+		authAndSub(http.HandlerFunc(alertEventHandler.List)))
 
-	// Authenticated routes — notification config
+	// Authenticated + subscribed routes — notification config
 	mux.Handle("GET "+b+"/notification-config",
-		middleware.Authenticate(http.HandlerFunc(notifConfigHandler.GetConfig)))
+		authAndSub(http.HandlerFunc(notifConfigHandler.GetConfig)))
 	mux.Handle("PUT "+b+"/notification-config",
-		middleware.Authenticate(http.HandlerFunc(notifConfigHandler.UpdateConfig)))
+		authAndSub(http.HandlerFunc(notifConfigHandler.UpdateConfig)))
 	mux.Handle("DELETE "+b+"/notification-config",
-		middleware.Authenticate(http.HandlerFunc(notifConfigHandler.DeleteConfig)))
+		authAndSub(http.HandlerFunc(notifConfigHandler.DeleteConfig)))
 	mux.Handle("POST "+b+"/notification-config/test",
-		middleware.Authenticate(http.HandlerFunc(notifConfigHandler.TestChannels)))
+		authAndSub(http.HandlerFunc(notifConfigHandler.TestChannels)))
 
-	// Authenticated routes — email digest
+	// Authenticated + subscribed routes — email digest
 	mux.Handle("POST "+b+"/email/setup",
-		middleware.Authenticate(http.HandlerFunc(emailDigestHandler.SetupEmail)))
+		authAndSub(http.HandlerFunc(emailDigestHandler.SetupEmail)))
 	mux.Handle("POST "+b+"/email/digest",
-		middleware.Authenticate(http.HandlerFunc(emailDigestHandler.SendDigest)))
+		authAndSub(http.HandlerFunc(emailDigestHandler.SendDigest)))
 
 	handler := corsMiddleware(mux)
 

backend-go/cmd/poller/main.go

@@ -62,6 +62,7 @@ func main() {
 		eth, alertRuleModel, alertEventModel, addressModel, notifConfigModel,
 		cfg.ResendAPIKey, cfg.EmailFrom,
 	)
+	digestSvc := services.NewEmailDigestService(cfg.ResendAPIKey, cfg.EmailFrom, alertEventModel, notifConfigModel)
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
@@ -78,12 +79,14 @@ func main() {
 	}()
 
 	interval := time.Duration(cfg.PollIntervalMS) * time.Millisecond
+	digestInterval := time.Duration(cfg.DigestIntervalHours) * time.Hour
 
 	log.Println(strings.Repeat("=", separatorWidth))
 	log.Println("Koin Ping Observer Poller Starting")
 	log.Println(strings.Repeat("=", separatorWidth))
 	log.Printf("RPC URL: %s", cfg.EthRPCURL)
 	log.Printf("Poll Interval: %dms (%ds)", cfg.PollIntervalMS, cfg.PollIntervalMS/msPerSecond)
+	log.Printf("Digest Interval: %dh", cfg.DigestIntervalHours)
 	log.Println(strings.Repeat("=", separatorWidth))
 
 	runCycle(ctx, observer, evaluator)
@@ -91,6 +94,9 @@ func main() {
 	ticker := time.NewTicker(interval)
 	defer ticker.Stop()
 
+	digestTicker := time.NewTicker(digestInterval)
+	defer digestTicker.Stop()
+
 	for {
 		select {
 		case <-ctx.Done():
@@ -99,6 +105,13 @@ func main() {
 			return
 		case <-ticker.C:
 			runCycle(ctx, observer, evaluator)
+		case <-digestTicker.C:
+			sent, digestErr := digestSvc.SendDigestsForAllUsers(ctx)
+			if digestErr != nil {
+				log.Printf("Email digest failed: %v", digestErr)
+			} else {
+				log.Printf("Sent %d email digests", sent)
+			}
 		}
 	}
 }

backend-go/go.mod

@@ -44,6 +44,7 @@ require (
 	github.com/planetscale/vtprotobuf v0.6.1-0.20240319094008-0393e58bdf10 // indirect
 	github.com/resend/resend-go/v3 v3.1.1 // indirect
 	github.com/spiffe/go-spiffe/v2 v2.6.0 // indirect
+	github.com/stripe/stripe-go/v82 v82.5.1 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/contrib/detectors/gcp v1.39.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.61.0 // indirect

backend-go/go.sum

@@ -101,6 +101,8 @@ github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UV
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+github.com/stripe/stripe-go/v82 v82.5.1 h1:05q6ZDKoe8PLMpQV072obF74HCgP4XJeJYoNuRSX2+8=
+github.com/stripe/stripe-go/v82 v82.5.1/go.mod h1:majCQX6AfObAvJiHraPi/5udwHi4ojRvJnnxckvHrX8=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
 go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=

backend-go/infra/migrations/004_alert_event_dedup.sql

@@ -0,0 +1,3 @@
+CREATE UNIQUE INDEX IF NOT EXISTS idx_alert_events_dedup
+    ON alert_events (alert_rule_id, tx_hash)
+    WHERE tx_hash IS NOT NULL;

backend-go/infra/migrations/005_create_users_table.sql

@@ -0,0 +1,13 @@
+-- Migration 005: Create users table with UUID primary key
+-- This establishes a local user record for each Firebase-authenticated user.
+
+CREATE TABLE IF NOT EXISTS users (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  firebase_uid VARCHAR(128) NOT NULL UNIQUE,
+  email VARCHAR(255) NOT NULL,
+  display_name VARCHAR(255),
+  created_at TIMESTAMP DEFAULT NOW(),
+  updated_at TIMESTAMP DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_users_firebase_uid ON users(firebase_uid);

backend-go/infra/migrations/006_migrate_user_ids_to_uuid.sql

@@ -0,0 +1,73 @@
+-- Migration 006: Migrate user_id columns from Firebase UID strings to user UUIDs
+--
+-- Prerequisites: migration 005 (users table) must be applied first.
+-- This migration backfills the users table from existing data, then swaps the
+-- VARCHAR user_id columns for UUID foreign keys referencing users(id).
+
+BEGIN;
+
+-- 1. Backfill users table from existing Firebase UIDs in addresses
+INSERT INTO users (firebase_uid, email)
+  SELECT DISTINCT user_id, ''
+  FROM addresses
+  WHERE user_id IS NOT NULL
+ON CONFLICT (firebase_uid) DO NOTHING;
+
+-- 2. Backfill from notification configs (catches users with configs but no addresses)
+INSERT INTO users (firebase_uid, email)
+  SELECT DISTINCT user_id, ''
+  FROM user_notification_configs
+  WHERE user_id IS NOT NULL
+ON CONFLICT (firebase_uid) DO NOTHING;
+
+-- ============================================================
+-- 3. Migrate addresses.user_id from VARCHAR to UUID
+-- ============================================================
+
+ALTER TABLE addresses ADD COLUMN user_uuid UUID;
+
+UPDATE addresses a
+SET user_uuid = u.id
+FROM users u
+WHERE u.firebase_uid = a.user_id;
+
+-- Drop old constraints and column
+ALTER TABLE addresses DROP CONSTRAINT IF EXISTS addresses_user_id_address_key;
+DROP INDEX IF EXISTS idx_addresses_user_id;
+ALTER TABLE addresses DROP COLUMN user_id;
+
+-- Rename and constrain
+ALTER TABLE addresses RENAME COLUMN user_uuid TO user_id;
+ALTER TABLE addresses ALTER COLUMN user_id SET NOT NULL;
+ALTER TABLE addresses ADD CONSTRAINT fk_addresses_user
+  FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;
+ALTER TABLE addresses ADD CONSTRAINT addresses_user_id_address_key
+  UNIQUE (user_id, address);
+CREATE INDEX idx_addresses_user_id ON addresses(user_id);
+
+-- ============================================================
+-- 4. Migrate user_notification_configs.user_id from VARCHAR to UUID
+-- ============================================================
+
+-- Drop the PK first (it's on user_id)
+ALTER TABLE user_notification_configs DROP CONSTRAINT IF EXISTS user_notification_configs_pkey;
+DROP INDEX IF EXISTS idx_notification_configs_enabled;
+
+ALTER TABLE user_notification_configs ADD COLUMN user_uuid UUID;
+
+UPDATE user_notification_configs nc
+SET user_uuid = u.id
+FROM users u
+WHERE u.firebase_uid = nc.user_id;
+
+ALTER TABLE user_notification_configs DROP COLUMN user_id;
+ALTER TABLE user_notification_configs RENAME COLUMN user_uuid TO user_id;
+ALTER TABLE user_notification_configs ALTER COLUMN user_id SET NOT NULL;
+ALTER TABLE user_notification_configs ADD CONSTRAINT user_notification_configs_pkey
+  PRIMARY KEY (user_id);
+ALTER TABLE user_notification_configs ADD CONSTRAINT fk_notification_configs_user
+  FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;
+CREATE INDEX idx_notification_configs_enabled
+  ON user_notification_configs(notification_enabled);
+
+COMMIT;

backend-go/infra/migrations/007_add_stripe_to_users.sql

@@ -0,0 +1,8 @@
+-- Migration 007: Add Stripe subscription fields to users table
+
+ALTER TABLE users ADD COLUMN IF NOT EXISTS stripe_customer_id VARCHAR(255);
+ALTER TABLE users ADD COLUMN IF NOT EXISTS stripe_subscription_id VARCHAR(255);
+ALTER TABLE users ADD COLUMN IF NOT EXISTS subscription_status VARCHAR(50) DEFAULT 'none';
+ALTER TABLE users ADD COLUMN IF NOT EXISTS subscription_created_at TIMESTAMP;
+
+CREATE INDEX IF NOT EXISTS idx_users_stripe_customer_id ON users(stripe_customer_id);

backend-go/infra/schema.sql

@@ -4,15 +4,28 @@ DROP TABLE IF EXISTS alert_rules CASCADE;
 DROP TABLE IF EXISTS address_checkpoints CASCADE;
 DROP TABLE IF EXISTS user_notification_configs CASCADE;
 DROP TABLE IF EXISTS addresses CASCADE;
+DROP TABLE IF EXISTS users CASCADE;
+
+CREATE TABLE users (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  firebase_uid VARCHAR(128) NOT NULL UNIQUE,
+  email VARCHAR(255) NOT NULL,
+  display_name VARCHAR(255),
+  stripe_customer_id VARCHAR(255),
+  stripe_subscription_id VARCHAR(255),
+  subscription_status VARCHAR(50) DEFAULT 'none',
+  subscription_created_at TIMESTAMP,
+  created_at TIMESTAMP DEFAULT NOW(),
+  updated_at TIMESTAMP DEFAULT NOW()
+);
 
 CREATE TABLE addresses (
   id SERIAL PRIMARY KEY,
-  user_id VARCHAR(128) NOT NULL,       -- Firebase user ID (multi-user support)
+  user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
   address VARCHAR(42) NOT NULL,        -- Ethereum address format (0x + 40 hex chars)
   label VARCHAR(255),                  -- Optional human-readable label
   created_at TIMESTAMP DEFAULT NOW(),
 
-  -- Unique users can track the same address independently
   UNIQUE(user_id, address)
 );
 
@@ -51,7 +64,7 @@ CREATE TABLE address_checkpoints (
 );
 
 CREATE TABLE user_notification_configs (
-  user_id VARCHAR(128) PRIMARY KEY,
+  user_id UUID PRIMARY KEY REFERENCES users(id) ON DELETE CASCADE,
   discord_webhook_url TEXT,            -- Discord webhook URL (nullable)
   telegram_chat_id VARCHAR(128),       -- Telegram chat ID (nullable)
   telegram_bot_token VARCHAR(255),     -- Telegram bot token (nullable)
@@ -63,6 +76,8 @@ CREATE TABLE user_notification_configs (
 );
 
 -- Create indexes for common queries
+CREATE INDEX idx_users_firebase_uid ON users(firebase_uid);
+CREATE INDEX idx_users_stripe_customer_id ON users(stripe_customer_id);
 CREATE INDEX idx_addresses_user_id ON addresses(user_id);
 CREATE INDEX idx_alert_rules_address_id ON alert_rules(address_id);
 CREATE INDEX idx_alert_rules_enabled ON alert_rules(enabled);

backend-go/internal/config/config.go

@@ -13,6 +13,7 @@ const (
 	defaultDBPort = 5432
 	defaultPollIntervalMS = 60000
 	minPollIntervalMS = 1000
+	defaultDigestIntervalHours = 24
 )
 
 type Config struct {
@@ -30,6 +31,12 @@ type Config struct {
 	NodeEnv           string
 	ResendAPIKey         string
 	EmailFrom            string
+	DigestIntervalHours  int
+	StripeSecretKey      string
+	StripeWebhookSecret  string
+	StripePriceID        string
+	StripePublishableKey string
+	FrontendURL          string
 }
 
 // Load reads configuration from environment variables and returns a Config.
@@ -49,6 +56,12 @@ func Load() (*Config, error) {
 		NodeEnv:           getEnv("NODE_ENV", "development"),
 		ResendAPIKey:        os.Getenv("RESEND_API_KEY"),
 		EmailFrom:           getEnv("EMAIL_FROM", "Koin Ping <alerts@koinping.com>"),
+		DigestIntervalHours:  getEnvInt("DIGEST_INTERVAL_HOURS", defaultDigestIntervalHours),
+		StripeSecretKey:      os.Getenv("STRIPE_SECRET_KEY"),
+		StripeWebhookSecret:  os.Getenv("STRIPE_WEBHOOK_SECRET"),
+		StripePriceID:        os.Getenv("STRIPE_PRICE_ID"),
+		StripePublishableKey: os.Getenv("STRIPE_PUBLISHABLE_KEY"),
+		FrontendURL:          getEnv("FRONTEND_URL", "http://localhost:3000"),
 	}
 
 	if cfg.PollIntervalMS < minPollIntervalMS {

backend-go/internal/database/postgres.go

@@ -1,4 +1,3 @@
-// Package database manages PostgreSQL connection pools.
 package database
 
 import (
@@ -11,21 +10,21 @@ import (
 )
 
 const (
-	// maxConnIdleSeconds is the maximum idle time for a connection.
+
 	maxConnIdleSeconds = 30
-	// maxConnLifetimeMinutes is the maximum lifetime for a connection.
+
 	maxConnLifetimeMinutes = 5
-	// connectTimeoutSeconds is the timeout for initial connection.
+
 	connectTimeoutSeconds = 10
-	// maxConns is the maximum number of connections in the pool.
+
 	maxConns = 20
-	// minConns is the minimum number of connections in the pool.
+
 	minConns = 2
 )
 
 var pool *pgxpool.Pool //nolint:gochecknoglobals
 
-// Connect establishes a PostgreSQL connection pool using the given DSN.
+// establishPostgreSQL connection pool using the given DSN.
 func Connect(dsn string) (*pgxpool.Pool, error) {
 	cfg, err := pgxpool.ParseConfig(dsn)
 	if err != nil {
@@ -57,12 +56,10 @@ func Connect(dsn string) (*pgxpool.Pool, error) {
 	return p, nil
 }
 
-// Pool returns the global connection pool.
 func Pool() *pgxpool.Pool {
 	return pool
 }
 
-// Close closes the global connection pool.
 func Close() {
 	if pool != nil {
 		pool.Close()

backend-go/internal/domain/types.go

@@ -1,9 +1,20 @@
-// Package domain defines core domain types shared across the application.
 package domain
 
 import "time"
 
-// Address represents a tracked Ethereum address.
+type User struct {
+	ID                    string     `json:"id"`
+	FirebaseUID           string     `json:"-"`
+	Email                 string     `json:"email"`
+	DisplayName           *string    `json:"display_name"`           //nolint:tagliatelle
+	StripeCustomerID      *string    `json:"-"`
+	StripeSubscriptionID  *string    `json:"-"`
+	SubscriptionStatus    string     `json:"subscription_status"`    //nolint:tagliatelle
+	SubscriptionCreatedAt *time.Time `json:"subscription_created_at,omitempty"` //nolint:tagliatelle
+	CreatedAt             time.Time  `json:"created_at"`             //nolint:tagliatelle
+	UpdatedAt             time.Time  `json:"updated_at"`             //nolint:tagliatelle
+}
+
 type Address struct {
 	ID        int       `json:"id"`
 	UserID    string    `json:"user_id"`    //nolint:tagliatelle
@@ -12,13 +23,10 @@ type Address struct {
 	CreatedAt time.Time `json:"created_at"` //nolint:tagliatelle
 }
 
-// AlertType identifies the kind of alert rule.
 type AlertType string
 
-// String implements fmt.Stringer.
 func (a AlertType) String() string { return string(a) }
 
-// Alert type constants define the supported alert triggers.
 const (
 	AlertIncomingTx    AlertType = "incoming_tx"
 	AlertOutgoingTx    AlertType = "outgoing_tx"
@@ -26,7 +34,6 @@ const (
 	AlertBalanceBelow  AlertType = "balance_below"
 )
 
-// ValidAlertTypes lists all alert types accepted by the API.
 var ValidAlertTypes = []AlertType{ //nolint:gochecknoglobals
 	AlertIncomingTx,
 	AlertOutgoingTx,
@@ -62,7 +69,6 @@ func IsThresholdRequired(t AlertType) bool {
 	return false
 }
 
-// AlertRule represents a user-defined alert rule for an address.
 type AlertRule struct {
 	ID        int       `json:"id"`
 	AddressID int       `json:"address_id"` //nolint:tagliatelle
@@ -72,7 +78,6 @@ type AlertRule struct {
 	CreatedAt time.Time `json:"created_at"` //nolint:tagliatelle
 }
 
-// AlertEvent represents a fired alert event stored for history.
 type AlertEvent struct {
 	ID           int       `json:"id"`
 	AlertRuleID  int       `json:"alert_rule_id"`   //nolint:tagliatelle
@@ -82,7 +87,6 @@ type AlertEvent struct {
 	Timestamp    time.Time `json:"timestamp"`
 }
 
-// AddressCheckpoint tracks the last block checked for an address.
 type AddressCheckpoint struct {
 	AddressID        int       `json:"address_id"`         //nolint:tagliatelle
 	LastCheckedBlock int       `json:"last_checked_block"` //nolint:tagliatelle
@@ -119,21 +123,29 @@ type NormalizedTx struct {
 	Value          string  `json:"value"` // Wei as string for precision
 	BlockNumber    int     `json:"block_number"`    //nolint:tagliatelle
 	BlockTimestamp int64   `json:"block_timestamp"` //nolint:tagliatelle
+
+	// ERC-20 token transfer fields (nil for native ETH transfers)
+	TokenContract *string `json:"token_contract,omitempty"` //nolint:tagliatelle
+	TokenSymbol   *string `json:"token_symbol,omitempty"`   //nolint:tagliatelle
+	TokenDecimals *int    `json:"token_decimals,omitempty"` //nolint:tagliatelle
+	TokenValue    *string `json:"token_value,omitempty"`    //nolint:tagliatelle
+}
+
+// IsTokenTransfer returns true if this transaction represents an ERC-20 token transfer.
+func (tx NormalizedTx) IsTokenTransfer() bool {
+	return tx.TokenContract != nil
 }
 
-// Direction indicates whether a transaction is incoming or outgoing.
 type Direction string
 
 // String implements fmt.Stringer.
 func (d Direction) String() string { return string(d) }
 
-// Direction constants indicate the flow of a transaction relative to a watched address.
 const (
 	DirectionIncoming Direction = "incoming"
 	DirectionOutgoing Direction = "outgoing"
 )
 
-// ObservedTx is a NormalizedTx enriched with address and direction context.
 type ObservedTx struct {
 	NormalizedTx
 	AddressID int       `json:"address_id"` //nolint:tagliatelle

backend-go/internal/firebase/admin.go

@@ -1,4 +1,3 @@
-// Package firebase provides Firebase authentication integration.
 package firebase
 
 import (
@@ -17,7 +16,6 @@ var ( //nolint:gochecknoglobals
 	errInit    error        //nolint:gochecknoglobals
 )
 
-// Init initializes the Firebase app and auth client using the given project ID.
 func Init(projectID string) error {
 	once.Do(func() {
 		ctx := context.Background()
@@ -48,7 +46,6 @@ func Init(projectID string) error {
 	return errInit
 }
 
-// Auth returns the initialized Firebase auth client.
 func Auth() *auth.Client {
 	return authClient
 }

backend-go/internal/handlers/address.go

@@ -15,17 +15,14 @@ import (
 
 var ethAddressRe = regexp.MustCompile(`^0x[a-fA-F0-9]{40}$`)
 
-// AddressHandler handles HTTP requests for address management.
 type AddressHandler struct {
 	addresses *models.AddressModel
 }
 
-// NewAddressHandler creates a new AddressHandler.
 func NewAddressHandler(addresses *models.AddressModel) *AddressHandler {
 	return &AddressHandler{addresses: addresses}
 }
 
-// Create handles POST requests to add a new tracked address.
 func (h *AddressHandler) Create(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.GetUserID(r.Context())
 
@@ -92,6 +89,44 @@ func (h *AddressHandler) List(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, addresses)
 }
 
+//  handles PATCH requests to update an address label.
+func (h *AddressHandler) UpdateLabel(w http.ResponseWriter, r *http.Request) {
+	userID := middleware.GetUserID(r.Context())
+	addressID, ok := parseIntParam(r.PathValue("addressId"))
+	if !ok {
+		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid address ID")
+
+		return
+	}
+
+	var body struct {
+		Label *string `json:"label"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid request body")
+
+		return
+	}
+
+	log.Printf("User %s updating label for address ID: %d", userID, addressID)
+
+	addr, err := h.addresses.UpdateLabel(r.Context(), addressID, userID, body.Label)
+	if err != nil {
+		log.Printf("Error updating address label: %v", err)
+		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to update address")
+
+		return
+	}
+
+	if addr == nil {
+		writeError(w, http.StatusNotFound, "NOT_FOUND", "Address not found")
+
+		return
+	}
+
+	writeJSON(w, http.StatusOK, addr)
+}
+
 // Remove handles DELETE requests to remove a tracked address.
 func (h *AddressHandler) Remove(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.GetUserID(r.Context())

backend-go/internal/handlers/alert_event.go

@@ -4,7 +4,6 @@ import (
 	"log"
 	"net/http"
 	"strconv"
-	"time"
 
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 	"github.com/kjannette/koin-ping/backend-go/internal/middleware"
@@ -51,45 +50,9 @@ func (h *AlertEventHandler) List(w http.ResponseWriter, r *http.Request) {
 
 	log.Printf("Found %d alert events for user", len(events))
 
-	// MVP scaffolding: return mock data if DB is empty
-	if len(events) == 0 {
-		events = mockEvents(limit)
+	if events == nil {
+		events = []domain.AlertEvent{}
 	}
 
 	writeJSON(w, http.StatusOK, events)
 }
-
-func mockEvents(limit int) []domain.AlertEvent {
-	label1 := "Treasury Wallet"
-	label2 := "Cold Storage"
-
-	mocks := []domain.AlertEvent{
-		{
-			ID:           1,
-			AlertRuleID:  1,
-			Message:      "Incoming transaction detected: 5.5 ETH received",
-			AddressLabel: &label1,
-			Timestamp:    time.Now().Add(-2 * time.Hour),
-		},
-		{
-			ID:           2,           //nolint:mnd
-			AlertRuleID:  2,           //nolint:mnd
-			Message:      "Balance dropped below threshold: Current balance 8.2 ETH",
-			AddressLabel: &label1,
-			Timestamp:    time.Now().Add(-5 * time.Hour),
-		},
-		{
-			ID:           3,           //nolint:mnd
-			AlertRuleID:  3,           //nolint:mnd
-			Message:      "Outgoing transaction detected: 2.0 ETH sent",
-			AddressLabel: &label2,
-			Timestamp:    time.Now().Add(-24 * time.Hour),
-		},
-	}
-
-	if limit < len(mocks) {
-		return mocks[:limit]
-	}
-
-	return mocks
-}

backend-go/internal/handlers/alert_rule.go

@@ -14,21 +14,17 @@ import (
 	"github.com/kjannette/koin-ping/backend-go/internal/models"
 )
 
-// errThresholdFormat is returned when the threshold JSON cannot be decoded.
 var errThresholdFormat = errors.New("unsupported threshold format")
 
-// AlertRuleHandler handles HTTP requests for alert rule management.
 type AlertRuleHandler struct {
 	alertRules *models.AlertRuleModel
 	addresses  *models.AddressModel
 }
 
-// NewAlertRuleHandler creates a new AlertRuleHandler.
 func NewAlertRuleHandler(alertRules *models.AlertRuleModel, addresses *models.AddressModel) *AlertRuleHandler {
 	return &AlertRuleHandler{alertRules: alertRules, addresses: addresses}
 }
 
-// Create handles POST requests to create a new alert rule for an address.
 func (h *AlertRuleHandler) Create(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.GetUserID(r.Context())
 	addressID, ok := parseIntParam(r.PathValue("addressId"))

backend-go/internal/handlers/status.go

@@ -1,10 +1,67 @@
 package handlers
 
 import (
+	"log"
 	"net/http"
 	"time"
+
+	"github.com/kjannette/koin-ping/backend-go/internal/models"
 )
 
+// StatusHandler handles the system status endpoint.
+type StatusHandler struct {
+	checkpoints *models.CheckpointModel
+}
+
+// NewStatusHandler creates a new StatusHandler.
+func NewStatusHandler(checkpoints *models.CheckpointModel) *StatusHandler {
+	return &StatusHandler{checkpoints: checkpoints}
+}
+
+// GetStatus returns real-time system status derived from checkpoint data.
+func (h *StatusHandler) GetStatus(w http.ResponseWriter, r *http.Request) {
+	block, checkedAt, err := h.checkpoints.GetLatestBlock(r.Context())
+	if err != nil {
+		log.Printf("Error querying latest block: %v", err)
+		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to get system status")
+
+		return
+	}
+
+	latestBlock := 0
+	lag := 0
+	status := "starting"
+
+	if checkedAt != nil {
+		lag = int(time.Since(*checkedAt).Seconds())
+		if lag > 600 { //nolint:mnd
+			status = "idle"
+		} else {
+			status = "active"
+		}
+	}
+
+	if block != nil {
+		latestBlock = *block
+	}
+
+	writeJSON(w, http.StatusOK, map[string]interface{}{
+		"status":        status,
+		"latestBlock":   latestBlock,
+		"lag":           lag,
+		"lastCheckedAt": checkedAtStr(checkedAt),
+		"timestamp":     time.Now().UTC().Format(time.RFC3339),
+	})
+}
+
+func checkedAtStr(t *time.Time) string {
+	if t == nil {
+		return ""
+	}
+
+	return t.UTC().Format(time.RFC3339)
+}
+
 func HealthCheck(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]interface{}{
 		"status":    "ok",
@@ -12,12 +69,3 @@ func HealthCheck(w http.ResponseWriter, r *http.Request) {
 		"service":   "koin-ping-backend",
 	})
 }
-
-func SystemStatus(w http.ResponseWriter, r *http.Request) {
-	writeJSON(w, http.StatusOK, map[string]interface{}{
-		"latestBlock": 0,
-		"lag":         0,
-		"status":      "healthy",
-		"timestamp":   time.Now().UTC().Format(time.RFC3339),
-	})
-}

backend-go/internal/handlers/stripe.go

@@ -0,0 +1,199 @@
+package handlers
+
+import (
+	"encoding/json"
+	"io"
+	"log"
+	"net/http"
+
+	"github.com/stripe/stripe-go/v82"
+	checkoutsession "github.com/stripe/stripe-go/v82/checkout/session"
+	"github.com/stripe/stripe-go/v82/webhook"
+
+	"github.com/kjannette/koin-ping/backend-go/internal/config"
+	"github.com/kjannette/koin-ping/backend-go/internal/middleware"
+	"github.com/kjannette/koin-ping/backend-go/internal/models"
+)
+
+const webhookMaxBodyBytes = 65536
+
+type StripeHandler struct {
+	users *models.UserModel
+	cfg   *config.Config
+}
+
+func NewStripeHandler(users *models.UserModel, cfg *config.Config) *StripeHandler {
+	stripe.Key = cfg.StripeSecretKey
+	return &StripeHandler{users: users, cfg: cfg}
+}
+
+// CreateCheckoutSession creates a Stripe Checkout session for the monthly subscription.
+func (h *StripeHandler) CreateCheckoutSession(w http.ResponseWriter, r *http.Request) {
+	userID := middleware.GetUserID(r.Context())
+
+	user, err := h.users.GetByID(r.Context(), userID)
+	if err != nil || user == nil {
+		log.Printf("Failed to get user %s: %v", userID, err)
+		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to load user")
+		return
+	}
+
+	params := &stripe.CheckoutSessionParams{
+		Mode: stripe.String(string(stripe.CheckoutSessionModeSubscription)),
+		LineItems: []*stripe.CheckoutSessionLineItemParams{
+			{
+				Price:    stripe.String(h.cfg.StripePriceID),
+				Quantity: stripe.Int64(1),
+			},
+		},
+		SuccessURL:        stripe.String(h.cfg.FrontendURL + "/subscribe?payment=success&session_id={CHECKOUT_SESSION_ID}"),
+		CancelURL:         stripe.String(h.cfg.FrontendURL + "/subscribe?payment=cancelled"),
+		ClientReferenceID: stripe.String(userID),
+		CustomerEmail:     stripe.String(user.Email),
+	}
+
+	if user.StripeCustomerID != nil && *user.StripeCustomerID != "" {
+		params.Customer = user.StripeCustomerID
+		params.CustomerEmail = nil
+	}
+
+	s, err := checkoutsession.New(params)
+	if err != nil {
+		log.Printf("Failed to create Stripe checkout session: %v", err)
+		writeError(w, http.StatusInternalServerError, "STRIPE_ERROR", "Failed to create checkout session")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]string{"url": s.URL})
+}
+
+// GetSubscriptionStatus returns the current user's subscription state.
+func (h *StripeHandler) GetSubscriptionStatus(w http.ResponseWriter, r *http.Request) {
+	userID := middleware.GetUserID(r.Context())
+
+	user, err := h.users.GetByID(r.Context(), userID)
+	if err != nil || user == nil {
+		log.Printf("Failed to get user %s: %v", userID, err)
+		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to load user")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]any{
+		"subscription_status":     user.SubscriptionStatus,
+		"subscription_created_at": user.SubscriptionCreatedAt,
+	})
+}
+
+// HandleWebhook processes incoming Stripe webhook events.
+// This endpoint must NOT require authentication (Stripe calls it directly).
+func (h *StripeHandler) HandleWebhook(w http.ResponseWriter, r *http.Request) {
+	payload, err := io.ReadAll(io.LimitReader(r.Body, webhookMaxBodyBytes))
+	if err != nil {
+		log.Printf("Error reading webhook body: %v", err)
+		w.WriteHeader(http.StatusServiceUnavailable)
+		return
+	}
+
+	sig := r.Header.Get("Stripe-Signature")
+	event, err := webhook.ConstructEvent(payload, sig, h.cfg.StripeWebhookSecret)
+	if err != nil {
+		log.Printf("Webhook signature verification failed: %v", err)
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	switch event.Type {
+	case "checkout.session.completed":
+		h.handleCheckoutCompleted(r, event)
+	case "customer.subscription.updated":
+		h.handleSubscriptionUpdated(r, event)
+	case "customer.subscription.deleted":
+		h.handleSubscriptionDeleted(r, event)
+	default:
+		log.Printf("Unhandled Stripe event type: %s", event.Type)
+	}
+
+	w.WriteHeader(http.StatusOK)
+}
+
+func (h *StripeHandler) handleCheckoutCompleted(r *http.Request, event stripe.Event) {
+	var session stripe.CheckoutSession
+	if err := json.Unmarshal(event.Data.Raw, &session); err != nil {
+		log.Printf("Error parsing checkout session: %v", err)
+		return
+	}
+
+	userID := session.ClientReferenceID
+	if userID == "" {
+		log.Println("Checkout session missing client_reference_id")
+		return
+	}
+
+	customerID := ""
+	if session.Customer != nil {
+		customerID = session.Customer.ID
+	}
+	subscriptionID := ""
+	if session.Subscription != nil {
+		subscriptionID = session.Subscription.ID
+	}
+
+	if customerID != "" {
+		if err := h.users.UpdateStripeCustomer(r.Context(), userID, customerID); err != nil {
+			log.Printf("Failed to save Stripe customer ID: %v", err)
+		}
+	}
+
+	if subscriptionID != "" && customerID != "" {
+		if err := h.users.ActivateSubscription(r.Context(), customerID, subscriptionID, "active"); err != nil {
+			log.Printf("Failed to activate subscription: %v", err)
+		}
+	}
+
+	log.Printf("Checkout completed for user %s, customer %s, subscription %s", userID, customerID, subscriptionID)
+}
+
+func (h *StripeHandler) handleSubscriptionUpdated(r *http.Request, event stripe.Event) {
+	var sub stripe.Subscription
+	if err := json.Unmarshal(event.Data.Raw, &sub); err != nil {
+		log.Printf("Error parsing subscription update: %v", err)
+		return
+	}
+
+	customerID := ""
+	if sub.Customer != nil {
+		customerID = sub.Customer.ID
+	}
+	if customerID == "" {
+		return
+	}
+
+	status := string(sub.Status)
+	if err := h.users.ActivateSubscription(r.Context(), customerID, sub.ID, status); err != nil {
+		log.Printf("Failed to update subscription status: %v", err)
+	}
+
+	log.Printf("Subscription %s updated to %s for customer %s", sub.ID, status, customerID)
+}
+
+func (h *StripeHandler) handleSubscriptionDeleted(r *http.Request, event stripe.Event) {
+	var sub stripe.Subscription
+	if err := json.Unmarshal(event.Data.Raw, &sub); err != nil {
+		log.Printf("Error parsing subscription deletion: %v", err)
+		return
+	}
+
+	customerID := ""
+	if sub.Customer != nil {
+		customerID = sub.Customer.ID
+	}
+	if customerID == "" {
+		return
+	}
+
+	if err := h.users.UpdateSubscriptionStatus(r.Context(), customerID, "canceled"); err != nil {
+		log.Printf("Failed to mark subscription canceled: %v", err)
+	}
+
+	log.Printf("Subscription canceled for customer %s", customerID)
+}

backend-go/internal/middleware/auth.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	fbauth "github.com/kjannette/koin-ping/backend-go/internal/firebase"
+	"github.com/kjannette/koin-ping/backend-go/internal/models"
 )
 
 type contextKey string
@@ -26,10 +27,14 @@ type errorResponse struct {
 func writeJSON(w http.ResponseWriter, status int, v interface{}) {
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(status)
-	json.NewEncoder(w).Encode(v)
+	json.NewEncoder(w).Encode(v) //nolint:errcheck
 }
 
-func Authenticate(next http.Handler) http.Handler {
+// Authenticate verifies the Firebase ID token and auto-provisions a local user
+// record. The local user UUID (not the Firebase UID) is placed into context so
+// all downstream handlers use it as the canonical user identifier.
+func Authenticate(userModel *models.UserModel) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			authHeader := r.Header.Get("Authorization")
 			if authHeader == "" || !strings.HasPrefix(authHeader, "Bearer ") {
@@ -72,16 +77,64 @@ func Authenticate(next http.Handler) http.Handler {
 				return
 			}
 
-		userID := decoded.UID
+			firebaseUID := decoded.UID
 			email, _ := decoded.Claims["email"].(string)
 
-		log.Printf("Token verified! User ID: %s, Email: %s", userID, email)
+			user, err := userModel.FindOrCreateByFirebaseUID(r.Context(), firebaseUID, email)
+			if err != nil {
+				log.Printf("Failed to provision local user for Firebase UID %s: %v", firebaseUID, err)
+				writeJSON(w, http.StatusInternalServerError, errorResponse{
+					Error:   "INTERNAL_ERROR",
+					Message: "Failed to initialize user account",
+				})
+				return
+			}
 
-		ctx := context.WithValue(r.Context(), UserIDKey, userID)
+			log.Printf("Token verified! User UUID: %s, Email: %s", user.ID, email)
+
+			ctx := context.WithValue(r.Context(), UserIDKey, user.ID)
 			ctx = context.WithValue(ctx, UserEmailKey, email)
 
 			next.ServeHTTP(w, r.WithContext(ctx))
 		})
+	}
+}
+
+// RequireSubscription blocks requests from users without an active subscription.
+// Must be applied after Authenticate.
+func RequireSubscription(userModel *models.UserModel) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			userID := GetUserID(r.Context())
+			if userID == "" {
+				writeJSON(w, http.StatusUnauthorized, errorResponse{
+					Error:   "UNAUTHORIZED",
+					Message: "Authentication required",
+				})
+				return
+			}
+
+			user, err := userModel.GetByID(r.Context(), userID)
+			if err != nil || user == nil {
+				log.Printf("RequireSubscription: failed to load user %s: %v", userID, err)
+				writeJSON(w, http.StatusInternalServerError, errorResponse{
+					Error:   "INTERNAL_ERROR",
+					Message: "Failed to verify subscription",
+				})
+				return
+			}
+
+			if user.SubscriptionStatus != "active" && user.SubscriptionStatus != "trialing" {
+				writeJSON(w, http.StatusForbidden, errorResponse{
+					Error:   "SUBSCRIPTION_REQUIRED",
+					Message: "An active subscription is required to use this feature",
+				})
+				return
+			}
+
+			next.ServeHTTP(w, r)
+		})
+	}
 }
 
 func GetUserID(ctx context.Context) string {

backend-go/internal/models/address.go

@@ -107,6 +107,24 @@ func (m *AddressModel) FindByID(ctx context.Context, id int, userID *string) (*d
 	return &a, nil
 }
 
+// UpdateLabel updates the label for an address owned by userID.
+// Returns nil, nil if no row matched (address not found or not owned by user).
+func (m *AddressModel) UpdateLabel(ctx context.Context, id int, userID string, label *string) (*domain.Address, error) {
+	var a domain.Address
+	err := m.pool.QueryRow(ctx,
+		`UPDATE addresses SET label = $3 WHERE id = $1 AND user_id = $2
+		 RETURNING id, user_id, address, label, created_at`,
+		id, userID, label,
+	).Scan(&a.ID, &a.UserID, &a.Address, &a.Label, &a.CreatedAt)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, nil
+		}
+		return nil, err
+	}
+	return &a, nil
+}
+
 func (m *AddressModel) Remove(ctx context.Context, id int, userID string) (bool, error) {
 	tag, err := m.pool.Exec(ctx,
 		`DELETE FROM addresses WHERE id = $1 AND user_id = $2`,

backend-go/internal/models/alert_event.go

@@ -2,7 +2,9 @@ package models
 
 import (
 	"context"
+	"errors"
 
+	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 )
@@ -71,10 +73,15 @@ func (m *AlertEventModel) Create(ctx context.Context, alertRuleID int, message s
 	err := m.pool.QueryRow(ctx,
 		`INSERT INTO alert_events (alert_rule_id, message, address_label, tx_hash)
 		 VALUES ($1, $2, $3, $4)
+		 ON CONFLICT DO NOTHING
 		 RETURNING id, alert_rule_id, message, address_label, tx_hash, timestamp`,
 		alertRuleID, message, addressLabel, txHash,
 	).Scan(&e.ID, &e.AlertRuleID, &e.Message, &e.AddressLabel, &e.TxHash, &e.Timestamp)
 	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			// Duplicate silently skipped by ON CONFLICT DO NOTHING
+			return nil, nil
+		}
 		return nil, err
 	}
 	return &e, nil

backend-go/internal/models/checkpoint.go

@@ -3,6 +3,7 @@ package models
 import (
 	"context"
 	"errors"
+	"time"
 
 	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
@@ -17,6 +18,20 @@ func NewCheckpointModel(pool *pgxpool.Pool) *CheckpointModel {
 	return &CheckpointModel{pool: pool}
 }
 
+// GetLatestBlock returns the highest last_checked_block and its timestamp across all addresses.
+// Returns nil, nil, nil when no checkpoints exist yet.
+func (m *CheckpointModel) GetLatestBlock(ctx context.Context) (*int, *time.Time, error) {
+	var block *int
+	var checkedAt *time.Time
+	err := m.pool.QueryRow(ctx,
+		`SELECT MAX(last_checked_block), MAX(last_checked_at) FROM address_checkpoints`,
+	).Scan(&block, &checkedAt)
+	if err != nil {
+		return nil, nil, err
+	}
+	return block, checkedAt, nil
+}
+
 // GetLastCheckedBlock returns the last checked block for an address, or -1 if never checked.
 func (m *CheckpointModel) GetLastCheckedBlock(ctx context.Context, addressID int) (int, bool, error) {
 	var block int

backend-go/internal/models/user.go

@@ -0,0 +1,89 @@
+package models
+
+import (
+	"context"
+	"errors"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+	"github.com/kjannette/koin-ping/backend-go/internal/domain"
+)
+
+type UserModel struct {
+	pool *pgxpool.Pool
+}
+
+func NewUserModel(pool *pgxpool.Pool) *UserModel {
+	return &UserModel{pool: pool}
+}
+
+const userColumns = `id, firebase_uid, email, display_name,
+	stripe_customer_id, stripe_subscription_id, subscription_status,
+	subscription_created_at, created_at, updated_at`
+
+func scanUser(row pgx.Row) (*domain.User, error) {
+	var u domain.User
+	err := row.Scan(
+		&u.ID, &u.FirebaseUID, &u.Email, &u.DisplayName,
+		&u.StripeCustomerID, &u.StripeSubscriptionID, &u.SubscriptionStatus,
+		&u.SubscriptionCreatedAt, &u.CreatedAt, &u.UpdatedAt,
+	)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, nil //nolint:nilnil
+		}
+		return nil, err
+	}
+	return &u, nil
+}
+
+// FindOrCreateByFirebaseUID returns the local user for a Firebase UID,
+// creating one if it doesn't exist yet. On conflict (returning user) the
+// updated_at timestamp is refreshed.
+func (m *UserModel) FindOrCreateByFirebaseUID(ctx context.Context, firebaseUID, email string) (*domain.User, error) {
+	row := m.pool.QueryRow(ctx,
+		`INSERT INTO users (firebase_uid, email)
+		 VALUES ($1, $2)
+		 ON CONFLICT (firebase_uid) DO UPDATE SET updated_at = NOW()
+		 RETURNING `+userColumns,
+		firebaseUID, email,
+	)
+	return scanUser(row)
+}
+
+func (m *UserModel) GetByID(ctx context.Context, id string) (*domain.User, error) {
+	row := m.pool.QueryRow(ctx,
+		`SELECT `+userColumns+` FROM users WHERE id = $1`, id,
+	)
+	return scanUser(row)
+}
+
+func (m *UserModel) UpdateStripeCustomer(ctx context.Context, userID, stripeCustomerID string) error {
+	_, err := m.pool.Exec(ctx,
+		`UPDATE users SET stripe_customer_id = $2, updated_at = NOW() WHERE id = $1`,
+		userID, stripeCustomerID,
+	)
+	return err
+}
+
+func (m *UserModel) ActivateSubscription(ctx context.Context, stripeCustomerID, subscriptionID, status string) error {
+	_, err := m.pool.Exec(ctx,
+		`UPDATE users
+		 SET stripe_subscription_id = $2,
+		     subscription_status = $3,
+		     subscription_created_at = COALESCE(subscription_created_at, NOW()),
+		     updated_at = NOW()
+		 WHERE stripe_customer_id = $1`,
+		stripeCustomerID, subscriptionID, status,
+	)
+	return err
+}
+
+func (m *UserModel) UpdateSubscriptionStatus(ctx context.Context, stripeCustomerID, status string) error {
+	_, err := m.pool.Exec(ctx,
+		`UPDATE users SET subscription_status = $2, updated_at = NOW()
+		 WHERE stripe_customer_id = $1`,
+		stripeCustomerID, status,
+	)
+	return err
+}

backend-go/internal/notifications/discord.go

@@ -2,6 +2,7 @@ package notifications
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
 	"log"
@@ -25,11 +26,15 @@ var discordHTTPClient = &http.Client{ //nolint:gochecknoglobals
 	Timeout: discordHTTPTimeoutSeconds * time.Second,
 }
 
-type AlertMetadata struct {
-	TxHash       string
-	AddressLabel string
-	AlertType    string
-	Address      string
+// DiscordNotifier sends alert notifications via a Discord webhook.
+type DiscordNotifier struct {
+	WebhookURL string
+}
+
+// Send implements Notifier for Discord.
+func (d *DiscordNotifier) Send(_ context.Context, message string, meta AlertMetadata) error {
+	_, err := SendDiscordNotification(d.WebhookURL, message, meta)
+	return err
 }
 
 type discordEmbed struct {

backend-go/internal/notifications/email.go

@@ -2,6 +2,7 @@ package notifications
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
 	"log"
@@ -9,6 +10,19 @@ import (
 	"time"
 )
 
+// EmailNotifier sends alert notifications via email (Resend).
+type EmailNotifier struct {
+	APIKey string
+	From   string
+	To     string
+}
+
+// Send implements Notifier for email.
+func (e *EmailNotifier) Send(_ context.Context, message string, meta AlertMetadata) error {
+	_, err := SendEmailNotification(e.APIKey, e.From, e.To, message, meta)
+	return err
+}
+
 const emailHTTPTimeoutSeconds = 10
 
 var emailHTTPClient = &http.Client{ //nolint:gochecknoglobals

backend-go/internal/notifications/notifier.go

@@ -0,0 +1,16 @@
+package notifications
+
+import "context"
+
+// AlertMetadata holds context about the alert being sent.
+type AlertMetadata struct {
+	TxHash       string
+	AddressLabel string
+	AlertType    string
+	Address      string
+}
+
+// Notifier is the interface implemented by all notification channels.
+type Notifier interface {
+	Send(ctx context.Context, message string, meta AlertMetadata) error
+}

backend-go/internal/notifications/slack.go

@@ -2,6 +2,7 @@ package notifications
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
 	"log"
@@ -9,6 +10,17 @@ import (
 	"time"
 )
 
+// SlackNotifier sends alert notifications via a Slack webhook.
+type SlackNotifier struct {
+	WebhookURL string
+}
+
+// Send implements Notifier for Slack.
+func (s *SlackNotifier) Send(_ context.Context, message string, meta AlertMetadata) error {
+	_, err := SendSlackNotification(s.WebhookURL, message, meta)
+	return err
+}
+
 const slackHTTPTimeoutSeconds = 10
 
 var slackHTTPClient = &http.Client{ //nolint:gochecknoglobals

backend-go/internal/notifications/telegram.go

@@ -2,6 +2,7 @@ package notifications
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
 	"log"
@@ -9,6 +10,18 @@ import (
 	"time"
 )
 
+// TelegramNotifier sends alert notifications via Telegram.
+type TelegramNotifier struct {
+	BotToken string
+	ChatID   string
+}
+
+// Send implements Notifier for Telegram.
+func (t *TelegramNotifier) Send(_ context.Context, message string, meta AlertMetadata) error {
+	_, err := SendTelegramNotification(t.BotToken, t.ChatID, message, meta)
+	return err
+}
+
 const telegramHTTPTimeoutSeconds = 10
 
 var telegramHTTPClient = &http.Client{ //nolint:gochecknoglobals

backend-go/internal/protocols/ethereum/jsonrpc.go

@@ -4,7 +4,9 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
+	"log"
 	"math/big"
 	"net/http"
 	"strings"
@@ -13,7 +15,11 @@ import (
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 )
 
-const rpcTimeoutMS = 30000
+const (
+	rpcTimeoutMS    = 30000
+	rpcMaxRetries   = 3
+	rpcRetryBaseMS  = 1000
+)
 
 type JsonRpcEthereum struct {
 	rpcURL string
@@ -66,6 +72,44 @@ func (j *JsonRpcEthereum) callRPC(ctx context.Context, method string, params ...
 		return nil, fmt.Errorf("marshal RPC request: %w", err)
 	}
 
+	return j.callWithRetry(ctx, method, body)
+}
+
+// callWithRetry executes a JSON-RPC POST with exponential backoff on transient errors.
+// It retries on network errors, HTTP 429, and HTTP 5xx. It does NOT retry on RPC-level
+// errors or other 4xx responses (those are permanent failures).
+func (j *JsonRpcEthereum) callWithRetry(ctx context.Context, method string, body []byte) (json.RawMessage, error) {
+	var lastErr error
+	for attempt := range rpcMaxRetries {
+		if attempt > 0 {
+			wait := time.Duration(rpcRetryBaseMS*(1<<(attempt-1))) * time.Millisecond
+			select {
+			case <-ctx.Done():
+				return nil, ctx.Err()
+			case <-time.After(wait):
+			}
+			log.Printf("Retrying RPC call [%s] (attempt %d/%d)", method, attempt+1, rpcMaxRetries)
+		}
+
+		result, err := j.doRPCCall(ctx, method, body)
+		if err == nil {
+			return result, nil
+		}
+
+		lastErr = err
+
+		// Permanent errors: do not retry
+		if isPermanentRPCError(err) {
+			return nil, err
+		}
+
+		log.Printf("Transient RPC error [%s] (attempt %d/%d): %v", method, attempt+1, rpcMaxRetries, err)
+	}
+
+	return nil, lastErr
+}
+
+func (j *JsonRpcEthereum) doRPCCall(ctx context.Context, method string, body []byte) (json.RawMessage, error) {
 	req, err := http.NewRequestWithContext(ctx, http.MethodPost, j.rpcURL, bytes.NewReader(body))
 	if err != nil {
 		return nil, fmt.Errorf("create RPC request: %w", err)
@@ -78,8 +122,13 @@ func (j *JsonRpcEthereum) callRPC(ctx context.Context, method string, params ...
 	}
 	defer resp.Body.Close()
 
+	// 429 and 5xx are transient; other non-200 are permanent.
 	if resp.StatusCode != http.StatusOK {
-		return nil, fmt.Errorf("HTTP %d: %s for %s", resp.StatusCode, resp.Status, method)
+		err := fmt.Errorf("HTTP %d: %s for %s", resp.StatusCode, resp.Status, method)
+		if resp.StatusCode == http.StatusTooManyRequests || resp.StatusCode >= 500 { //nolint:mnd
+			return nil, err // transient — will be retried
+		}
+		return nil, &permanentRPCError{err}
 	}
 
 	var rpcResp rpcResponse
@@ -88,12 +137,25 @@ func (j *JsonRpcEthereum) callRPC(ctx context.Context, method string, params ...
 	}
 
 	if rpcResp.Error != nil {
-		return nil, fmt.Errorf("RPC Error [%s]: %s (code: %d)", method, rpcResp.Error.Message, rpcResp.Error.Code)
+		// RPC-level errors are permanent (bad params, unsupported method, etc.)
+		return nil, &permanentRPCError{
+			fmt.Errorf("RPC Error [%s]: %s (code: %d)", method, rpcResp.Error.Message, rpcResp.Error.Code),
+		}
 	}
 
 	return rpcResp.Result, nil
 }
 
+type permanentRPCError struct{ cause error }
+
+func (e *permanentRPCError) Error() string { return e.cause.Error() }
+func (e *permanentRPCError) Unwrap() error { return e.cause }
+
+func isPermanentRPCError(err error) bool {
+	var p *permanentRPCError
+	return errors.As(err, &p)
+}
+
 func (j *JsonRpcEthereum) GetLatestBlockNumber(ctx context.Context) (int, error) {
 	result, err := j.callRPC(ctx, "eth_blockNumber")
 	if err != nil {
@@ -180,6 +242,132 @@ func (j *JsonRpcEthereum) GetBalance(ctx context.Context, address string) (strin
 	return hexToDecimalString(hexBalance), nil
 }
 
+const erc20TransferTopic = "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"
+
+const minTransferTopics = 3
+
+type rpcLog struct {
+	Address     string   `json:"address"`
+	Topics      []string `json:"topics"`
+	Data        string   `json:"data"`
+	BlockNumber string   `json:"blockNumber"`
+	TxHash      string   `json:"transactionHash"`
+}
+
+// GetTokenTransfers fetches ERC-20 Transfer events for a given address
+// across a block range, covering both incoming and outgoing transfers.
+func (j *JsonRpcEthereum) GetTokenTransfers(ctx context.Context, fromBlock, toBlock int, address string) ([]domain.NormalizedTx, error) {
+	paddedAddr := padAddress(address)
+	hexFrom := fmt.Sprintf("0x%x", fromBlock)
+	hexTo := fmt.Sprintf("0x%x", toBlock)
+
+	incomingLogs, err := j.getTransferLogs(ctx, hexFrom, hexTo, "", paddedAddr)
+	if err != nil {
+		return nil, fmt.Errorf("fetch incoming token transfers: %w", err)
+	}
+
+	outgoingLogs, err := j.getTransferLogs(ctx, hexFrom, hexTo, paddedAddr, "")
+	if err != nil {
+		return nil, fmt.Errorf("fetch outgoing token transfers: %w", err)
+	}
+
+	seen := make(map[string]bool)
+	var txs []domain.NormalizedTx
+
+	for _, entry := range append(incomingLogs, outgoingLogs...) {
+		key := entry.TxHash + "|" + entry.Address + "|" + entry.Data
+		if seen[key] {
+			continue
+		}
+		seen[key] = true
+
+		tx, parseErr := parseTransferLog(entry)
+		if parseErr != nil {
+			log.Printf("Skipping unparseable transfer log in tx %s: %v", entry.TxHash, parseErr)
+			continue
+		}
+		txs = append(txs, tx)
+	}
+
+	return txs, nil
+}
+
+func (j *JsonRpcEthereum) getTransferLogs(ctx context.Context, fromBlock, toBlock, fromAddr, toAddr string) ([]rpcLog, error) {
+	topics := make([]interface{}, minTransferTopics)
+	topics[0] = erc20TransferTopic
+
+	if fromAddr != "" {
+		topics[1] = fromAddr
+	}
+	if toAddr != "" {
+		topics[2] = toAddr
+	}
+
+	filter := map[string]interface{}{
+		"fromBlock": fromBlock,
+		"toBlock":   toBlock,
+		"topics":    topics,
+	}
+
+	result, err := j.callRPC(ctx, "eth_getLogs", filter)
+	if err != nil {
+		return nil, err
+	}
+
+	var logs []rpcLog
+	if err := json.Unmarshal(result, &logs); err != nil {
+		return nil, fmt.Errorf("unmarshal logs: %w", err)
+	}
+
+	return logs, nil
+}
+
+func parseTransferLog(entry rpcLog) (domain.NormalizedTx, error) {
+	if len(entry.Topics) < minTransferTopics {
+		return domain.NormalizedTx{}, fmt.Errorf("transfer log has %d topics, expected >= 3", len(entry.Topics))
+	}
+
+	from := topicToAddress(entry.Topics[1])
+	to := topicToAddress(entry.Topics[2])
+	tokenValue := hexToDecimalString(entry.Data)
+	blockNumber, _ := hexToInt(entry.BlockNumber)
+
+	contractAddr := strings.ToLower(entry.Address)
+	tokenInfo, known := LookupToken(contractAddr)
+
+	tx := domain.NormalizedTx{
+		Hash:          entry.TxHash,
+		From:          from,
+		To:            &to,
+		Value:         "0",
+		BlockNumber:   blockNumber,
+		TokenContract: &contractAddr,
+		TokenValue:    &tokenValue,
+	}
+
+	if known {
+		tx.TokenSymbol = &tokenInfo.Symbol
+		tx.TokenDecimals = &tokenInfo.Decimals
+	}
+
+	return tx, nil
+}
+
+func padAddress(addr string) string {
+	clean := strings.TrimPrefix(strings.ToLower(addr), "0x")
+	const addressHexLen = 64
+	return "0x" + strings.Repeat("0", addressHexLen-len(clean)) + clean
+}
+
+func topicToAddress(topic string) string {
+	clean := strings.TrimPrefix(topic, "0x")
+	const ethAddrLen = 40
+	if len(clean) > ethAddrLen {
+		clean = clean[len(clean)-ethAddrLen:]
+	}
+	return "0x" + strings.ToLower(clean)
+}
+
 func hexToInt(hex string) (int, error) {
 	hex = strings.TrimPrefix(hex, "0x")
 	n, ok := new(big.Int).SetString(hex, 16)

backend-go/internal/protocols/ethereum/observer.go

@@ -12,4 +12,5 @@ type EthereumObserver interface {
 	GetLatestBlockNumber(ctx context.Context) (int, error)
 	GetBlockTransactions(ctx context.Context, blockNumber int) ([]domain.NormalizedTx, error)
 	GetBalance(ctx context.Context, address string) (string, error)
+	GetTokenTransfers(ctx context.Context, fromBlock, toBlock int, address string) ([]domain.NormalizedTx, error)
 }

backend-go/internal/protocols/ethereum/tokens.go

@@ -0,0 +1,34 @@
+package ethereum
+
+import "strings"
+
+// TokenInfo holds metadata for a known ERC-20 token contract.
+type TokenInfo struct {
+	Symbol   string
+	Decimals int
+}
+
+//nolint:gochecknoglobals
+var wellKnownTokens = map[string]TokenInfo{
+	"0xdac17f958d2ee523a2206206994597c13d831ec7": {Symbol: "USDT", Decimals: 6},
+	"0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48": {Symbol: "USDC", Decimals: 6},
+	"0x6b175474e89094c44da98b954eedeac495271d0f": {Symbol: "DAI", Decimals: 18},
+	"0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2": {Symbol: "WETH", Decimals: 18},
+	"0x2260fac5e5542a773aa44fbcfedf7c193bc2c599": {Symbol: "WBTC", Decimals: 8},
+	"0x514910771af9ca656af840dff83e8264ecf986ca": {Symbol: "LINK", Decimals: 18},
+	"0x1f9840a85d5af5bf1d1762f925bdaddc4201f984": {Symbol: "UNI", Decimals: 18},
+	"0x7fc66500c84a76ad7e9c93437bfc5ac33e2ddae9": {Symbol: "AAVE", Decimals: 18},
+	"0x95ad61b0a150d79219dcf64e1e6cc01f0b64c4ce": {Symbol: "SHIB", Decimals: 18},
+	"0x6982508145454ce325ddbe47a25d4ec3d2311933": {Symbol: "PEPE", Decimals: 18},
+	"0xb8c77482e45f1f44de1745f52c74426c631bdd52": {Symbol: "BNB", Decimals: 18},
+	"0x4fabb145d64652a948d72533023f6e7a623c7c53": {Symbol: "BUSD", Decimals: 18},
+	"0x75231f58b43240c9718dd58b4967c5114342a86c": {Symbol: "OKB", Decimals: 18},
+	"0x582d872a1b094fc48f5de31d3b73f2d9be47def1": {Symbol: "TON", Decimals: 9},
+	"0x4d224452801aced8b2f0aebe155379bb5d594381": {Symbol: "APE", Decimals: 18},
+}
+
+// LookupToken returns metadata for a known token contract, if found.
+func LookupToken(contractAddress string) (TokenInfo, bool) {
+	info, ok := wellKnownTokens[strings.ToLower(contractAddress)]
+	return info, ok
+}

backend-go/internal/services/evaluator.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"log"
+	"time"
 
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 	"github.com/kjannette/koin-ping/backend-go/internal/models"
@@ -12,6 +13,12 @@ import (
 	"github.com/kjannette/koin-ping/backend-go/internal/wei"
 )
 
+const (
+	notificationTimeout    = 30 * time.Second
+	notificationMaxRetries = 3
+	notificationRetryBase  = time.Second
+)
+
 type EvaluatorService struct {
 	eth          ethereum.EthereumObserver
 	alertRules   *models.AlertRuleModel
@@ -167,25 +174,85 @@ func (s *EvaluatorService) fireAlert(ctx context.Context, rule domain.AlertRule,
 	message := s.buildMessage(rule, obs)
 	txHash := &obs.Hash
 
-	_, err = s.alertEvents.Create(ctx, rule.ID, message, &addressLabel, txHash)
+	event, err := s.alertEvents.Create(ctx, rule.ID, message, &addressLabel, txHash)
 	if err != nil {
 		return err
 	}
 
+	if event == nil {
+		log.Printf("[ALERT DEDUP] Rule %d (%s) - duplicate event skipped for TX: %s", rule.ID, rule.Type, obs.Hash)
+		return nil
+	}
+
 	log.Printf("[ALERT FIRED] Rule %d (%s) - %s - TX: %s", rule.ID, rule.Type, message, obs.Hash)
 
-	// Send Discord notification (non-fatal on failure)
 	if addr != nil {
+		userID := addr.UserID
+		address := addr.Address
 		go func() {
-			s.sendNotification(
-				ctx, addr.UserID, message, obs, addressLabel, rule, addr.Address,
-			)
+			notifCtx, cancel := context.WithTimeout(context.Background(), notificationTimeout)
+			defer cancel()
+			s.sendNotification(notifCtx, userID, message, obs, addressLabel, rule, address)
 		}()
 	}
 
 	return nil
 }
 
+func (s *EvaluatorService) buildNotifiers(cfg *domain.NotificationConfig) []notifications.Notifier {
+	var notifiers []notifications.Notifier
+
+	if cfg.DiscordWebhookURL != nil && *cfg.DiscordWebhookURL != "" {
+		notifiers = append(notifiers, &notifications.DiscordNotifier{WebhookURL: *cfg.DiscordWebhookURL})
+	}
+
+	if cfg.TelegramBotToken != nil && *cfg.TelegramBotToken != "" &&
+		cfg.TelegramChatID != nil && *cfg.TelegramChatID != "" {
+		notifiers = append(notifiers, &notifications.TelegramNotifier{
+			BotToken: *cfg.TelegramBotToken,
+			ChatID:   *cfg.TelegramChatID,
+		})
+	}
+
+	if cfg.SlackWebhookURL != nil && *cfg.SlackWebhookURL != "" {
+		notifiers = append(notifiers, &notifications.SlackNotifier{WebhookURL: *cfg.SlackWebhookURL})
+	}
+
+	if cfg.Email != nil && *cfg.Email != "" {
+		notifiers = append(notifiers, &notifications.EmailNotifier{
+			APIKey: s.resendAPIKey,
+			From:   s.emailFrom,
+			To:     *cfg.Email,
+		})
+	}
+
+	return notifiers
+}
+
+func sendWithRetry(ctx context.Context, n notifications.Notifier, message string, meta notifications.AlertMetadata) error {
+	var lastErr error
+	for attempt := range notificationMaxRetries {
+		if attempt > 0 {
+			wait := notificationRetryBase * time.Duration(1<<(attempt-1))
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			case <-time.After(wait):
+			}
+		}
+
+		if err := n.Send(ctx, message, meta); err != nil {
+			log.Printf("Notification attempt %d/%d failed: %v", attempt+1, notificationMaxRetries, err)
+			lastErr = err
+			continue
+		}
+
+		return nil
+	}
+
+	return lastErr
+}
+
 func (s *EvaluatorService) sendNotification(ctx context.Context, userID, message string, obs domain.ObservedTx, addressLabel string, rule domain.AlertRule, address string) {
 	notifConfig, err := s.notifConfigs.GetConfig(ctx, userID)
 	if err != nil {
@@ -204,49 +271,20 @@ func (s *EvaluatorService) sendNotification(ctx context.Context, userID, message
 		Address:      address,
 	}
 
-	if notifConfig.DiscordWebhookURL != nil && *notifConfig.DiscordWebhookURL != "" {
-		sent, sendErr := notifications.SendDiscordNotification(*notifConfig.DiscordWebhookURL, message, meta)
-		if sendErr != nil || !sent {
-			log.Printf("Discord notification failed for user %s: %v", userID, sendErr)
+	for _, n := range s.buildNotifiers(notifConfig) {
+		if err := sendWithRetry(ctx, n, message, meta); err != nil {
+			log.Printf("Notification channel failed for user %s after retries: %v", userID, err)
 		} else {
-			log.Printf("Discord notification sent to user %s", userID)
-		}
-	}
-
-	if notifConfig.TelegramBotToken != nil && *notifConfig.TelegramBotToken != "" &&
-		notifConfig.TelegramChatID != nil && *notifConfig.TelegramChatID != "" {
-		sent, sendErr := notifications.SendTelegramNotification(
-			*notifConfig.TelegramBotToken, *notifConfig.TelegramChatID, message, meta,
-		)
-		if sendErr != nil || !sent {
-			log.Printf("Telegram notification failed for user %s: %v", userID, sendErr)
-		} else {
-			log.Printf("Telegram notification sent to user %s", userID)
-		}
-	}
-
-	if notifConfig.SlackWebhookURL != nil && *notifConfig.SlackWebhookURL != "" {
-		sent, sendErr := notifications.SendSlackNotification(*notifConfig.SlackWebhookURL, message, meta)
-		if sendErr != nil || !sent {
-			log.Printf("Slack notification failed for user %s: %v", userID, sendErr)
-		} else {
-			log.Printf("Slack notification sent to user %s", userID)
-		}
-	}
-
-	if notifConfig.Email != nil && *notifConfig.Email != "" {
-		sent, sendErr := notifications.SendEmailNotification(
-			s.resendAPIKey, s.emailFrom, *notifConfig.Email, message, meta,
-		)
-		if sendErr != nil || !sent {
-			log.Printf("Email notification failed for user %s: %v", userID, sendErr)
-		} else {
-			log.Printf("Email notification sent to user %s", userID)
+			log.Printf("Notification sent to user %s via %T", userID, n)
 		}
 	}
 }
 
 func (s *EvaluatorService) buildMessage(rule domain.AlertRule, obs domain.ObservedTx) string {
+	if obs.IsTokenTransfer() {
+		return s.buildTokenMessage(rule, obs)
+	}
+
 	switch rule.Type {
 	case domain.AlertIncomingTx:
 		ethStr, _ := wei.FormatAsEth(obs.Value, 4)
@@ -271,3 +309,36 @@ func (s *EvaluatorService) buildMessage(rule domain.AlertRule, obs domain.Observ
 		return "Alert triggered"
 	}
 }
+
+const defaultTokenDecimals = 18
+
+func (s *EvaluatorService) buildTokenMessage(rule domain.AlertRule, obs domain.ObservedTx) string {
+	symbol := "tokens"
+	if obs.TokenSymbol != nil {
+		symbol = *obs.TokenSymbol
+	}
+
+	amount := "unknown"
+	if obs.TokenValue != nil {
+		decimals := defaultTokenDecimals
+		if obs.TokenDecimals != nil {
+			decimals = *obs.TokenDecimals
+		}
+		amount = wei.FormatTokenAmount(*obs.TokenValue, decimals)
+	}
+
+	switch rule.Type {
+	case domain.AlertIncomingTx:
+		return fmt.Sprintf("Incoming transfer: %s %s received", amount, symbol)
+	case domain.AlertOutgoingTx:
+		return fmt.Sprintf("Outgoing transfer: %s %s sent", amount, symbol)
+	case domain.AlertLargeTransfer:
+		threshold := float64(0)
+		if rule.Threshold != nil {
+			threshold = *rule.Threshold
+		}
+		return fmt.Sprintf("Large token transfer: %s %s (threshold: %g)", amount, symbol, threshold)
+	default:
+		return fmt.Sprintf("Token transfer: %s %s", amount, symbol)
+	}
+}

backend-go/internal/services/observer.go

@@ -80,6 +80,15 @@ func (s *ObserverService) observeAddress(ctx context.Context, addr domain.Addres
 		}
 	}
 
+	tokenTxs, err := s.eth.GetTokenTransfers(ctx, startBlock, endBlock, addr.Address)
+	if err != nil {
+		log.Printf("Error fetching token transfers for %s: %v", addr.Address, err)
+	} else {
+		for _, tx := range tokenTxs {
+			observations = append(observations, createObservedTx(tx, addr))
+		}
+	}
+
 	if _, err := s.checkpoint.UpdateLastCheckedBlock(ctx, addr.ID, endBlock); err != nil {
 		return nil, err
 	}

backend-go/internal/wei/converter.go

@@ -98,3 +98,54 @@ func FormatAsEth(weiString string, decimals int) (string, error) {
 	}
 	return fmt.Sprintf("%.*f ETH", decimals, eth), nil
 }
+
+// FormatTokenAmount formats a raw token amount using the token's decimal places.
+// For example, 1000000 USDT (6 decimals) becomes "1".
+func FormatTokenAmount(rawValue string, tokenDecimals int) string {
+	if rawValue == "" || rawValue == "0" {
+		return "0"
+	}
+
+	n, ok := new(big.Int).SetString(rawValue, 10)
+	if !ok {
+		return "0"
+	}
+
+	divisor := new(big.Int).Exp(big.NewInt(10), big.NewInt(int64(tokenDecimals)), nil) //nolint:mnd
+	whole := new(big.Int).Div(n, divisor)
+	remainder := new(big.Int).Mod(n, divisor)
+
+	if remainder.Sign() == 0 {
+		return addThousandsSeparators(whole.String())
+	}
+
+	fracStr := fmt.Sprintf("%0*s", tokenDecimals, remainder.String())
+	fracStr = strings.TrimRight(fracStr, "0")
+	const maxDisplayDecimals = 4
+	if len(fracStr) > maxDisplayDecimals {
+		fracStr = fracStr[:maxDisplayDecimals]
+	}
+
+	return addThousandsSeparators(whole.String()) + "." + fracStr
+}
+
+func addThousandsSeparators(s string) string {
+	if len(s) <= 3 { //nolint:mnd
+		return s
+	}
+
+	var result strings.Builder
+	offset := len(s) % 3 //nolint:mnd
+	if offset > 0 {
+		result.WriteString(s[:offset])
+	}
+
+	for i := offset; i < len(s); i += 3 { //nolint:mnd
+		if result.Len() > 0 {
+			result.WriteByte(',')
+		}
+		result.WriteString(s[i : i+3]) //nolint:mnd
+	}
+
+	return result.String()
+}

frontend/src/App.jsx

@@ -3,6 +3,7 @@ import { useAuth } from "./contexts/AuthContext";
 import Navbar from "./components/Navbar";
 import Login from "./pages/Login";
 import Signup from "./pages/Signup";
+import Onboarding from "./pages/Onboarding";
 import Addresses from "./pages/Addresses";
 import Alerts from "./pages/Alerts";
 import AlertHistory from "./pages/AlertHistory";
@@ -15,6 +16,7 @@ export default function App() {
             <Routes>
                 <Route path="/login" element={<Login />} />
                 <Route path="/signup" element={<Signup />} />
+                <Route path="/subscribe" element={<Onboarding />} />
                 <Route path="*" element={<Navigate to="/login" />} />
             </Routes>
         );
@@ -27,7 +29,8 @@ export default function App() {
                 <Route path="/" element={<Addresses />} />
                 <Route path="/addresses" element={<Addresses />} />
                 <Route path="/alerts" element={<Alerts />} />
-                <Route path="/history" element={<AlertHistory />} />
+                <Route path="/alertevents" element={<AlertHistory />} />
+                <Route path="/subscribe" element={<Onboarding />} />
                 <Route path="*" element={<Navigate to="/addresses" />} />
             </Routes>
         </div>

frontend/src/api/addresses.jsx

@@ -80,6 +80,41 @@ export async function getAddresses() {
     }
 }
 
+/**
+ * Update an address (e.g. change its label)
+ * @param {number} addressId - Address ID to update
+ * @param {Object} data - Fields to update (e.g. { label: "New Label" })
+ * @returns {Promise<Object>} Updated address
+ */
+export async function updateAddress(addressId, data) {
+    try {
+        const headers = await getAuthHeaders();
+        const response = await fetch(`${API_BASE}/addresses/${addressId}`, {
+            method: "PATCH",
+            headers: headers,
+            body: JSON.stringify(data),
+        });
+
+        if (!response.ok) {
+            let errorMessage = "Failed to update address";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
+
+        return response.json();
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error("Cannot connect to server. Is the backend running?");
+        }
+        throw error;
+    }
+}
+
 /**
  * Delete a tracked address
  * @param {number} addressId - Address ID to delete

frontend/src/api/stripe.jsx

@@ -0,0 +1,27 @@
+import { getAuthHeaders } from "./authHeaders";
+import { API_BASE } from "./config";
+
+export async function createCheckoutSession() {
+    const headers = await getAuthHeaders();
+    const res = await fetch(`${API_BASE}/stripe/create-checkout-session`, {
+        method: "POST",
+        headers,
+    });
+    if (!res.ok) {
+        const data = await res.json();
+        throw new Error(data.message || "Failed to create checkout session");
+    }
+    return res.json();
+}
+
+export async function getSubscriptionStatus() {
+    const headers = await getAuthHeaders();
+    const res = await fetch(`${API_BASE}/stripe/subscription-status`, {
+        headers,
+    });
+    if (!res.ok) {
+        const data = await res.json();
+        throw new Error(data.message || "Failed to get subscription status");
+    }
+    return res.json();
+}

frontend/src/components/AddressForm.jsx

@@ -37,7 +37,7 @@ export default function AddressForm({ onSubmit }) {
                 placeholder="Treasury, Cold Wallet, etc."
             />
 
-            <Button type="submit" disabled={!canSubmit}>
+            <Button type="submit" disabled={!canSubmit} className="mt-md">
                 Add Address
             </Button>
         </form>

frontend/src/components/AlertForm.css

@@ -0,0 +1,7 @@
+.alert-form__options {
+  margin-bottom: 1rem;
+}
+
+.alert-form__radio {
+  display: block;
+}

frontend/src/components/AlertForm.jsx

@@ -1,6 +1,7 @@
 import { useState } from "react";
 import Input from "./Input";
 import Button from "./Button";
+import "./AlertForm.css";
 
 const ALERT_TYPES = [
     { value: "incoming_tx", label: "Incoming transaction" },
@@ -36,9 +37,9 @@ export default function AlertForm({ onSubmit }) {
 
     return (
         <form onSubmit={handleSubmit}>
-            <div style={{ marginBottom: "1rem" }}>
+            <div className="alert-form__options">
                 {ALERT_TYPES.map((opt) => (
-                    <label key={opt.value} style={{ display: "block" }}>
+                    <label key={opt.value} className="alert-form__radio">
                         <input
                             type="radio"
                             name="alertType"

frontend/src/components/Button.css

@@ -0,0 +1,14 @@
+.btn {
+  padding: 0.5rem 1rem;
+  font-size: 1rem;
+  border: none;
+  border-radius: var(--radius-md);
+  cursor: pointer;
+  color: var(--color-text);
+  transition: opacity 0.15s ease;
+}
+
+.btn:disabled {
+  opacity: 0.6;
+  cursor: not-allowed;
+}

frontend/src/components/Button.jsx

@@ -1,20 +1,19 @@
+import "./Button.css";
+
 export default function Button({
     children,
     onClick,
     disabled = false,
     type = "button",
+    variant = "primary",
+    className = "",
 }) {
     return (
         <button
             type={type}
             onClick={onClick}
             disabled={disabled}
-            style={{
-                padding: "0.5rem 1rem",
-                fontSize: "1rem",
-                cursor: disabled ? "not-allowed" : "pointer",
-                opacity: disabled ? 0.6 : 1,
-            }}
+            className={`btn btn--${variant} ${className}`}
         >
             {children}
         </button>

frontend/src/components/Input.css

@@ -0,0 +1,21 @@
+.input__label {
+  display: block;
+  margin: 0.8rem 0rem 0.4rem 0rem;
+  font-size: 0.9rem;
+}
+
+.input__control {
+  width: 100%;
+  padding: 0.5rem;
+  font-size: 1rem;
+  background-color: var(--color-bg-elevated);
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-md);
+  color: var(--color-text);
+}
+
+.input__control:focus {
+  outline: none;
+  border-color: var(--color-primary);
+  box-shadow: 0 0 0 2px rgba(0, 102, 204, 0.25);
+}

frontend/src/components/Input.jsx

@@ -1,3 +1,5 @@
+import "./Input.css";
+
 export default function Input({
     label,
     type = "text",
@@ -7,12 +9,12 @@ export default function Input({
     step,
     min,
     disabled = false,
+    required = false,
+    className = "",
 }) {
     return (
-        <label style={{ display: "block", marginBottom: "1rem" }}>
-            <div style={{ marginBottom: "0.25rem", fontSize: "0.9rem" }}>
-                {label}
-            </div>
+        <label className={`form-field ${className}`}>
+            <div className="input__label">{label}</div>
             <input
                 type={type}
                 value={value}
@@ -20,12 +22,9 @@ export default function Input({
                 step={step}
                 min={min}
                 disabled={disabled}
+                required={required}
                 onChange={(e) => onChange(e.target.value)}
-                style={{
-                    width: "100%",
-                    padding: "0.5rem",
-                    fontSize: "1rem",
-                }}
+                className="input__control"
             />
         </label>
     );

frontend/src/components/Navbar.css

@@ -0,0 +1,56 @@
+.navbar {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  padding: 1rem 2rem;
+  margin-bottom: 1.5rem;
+  background-color: var(--color-bg);
+  border-bottom: 1px solid var(--color-border-light);
+}
+
+.navbar__brand {
+  font-weight: 700;
+  font-size: 1.4rem;
+  color: var(--color-brand);
+  margin-right: 2rem;
+  letter-spacing: 0.5px;
+}
+
+.navbar__links {
+  display: flex;
+  gap: 0.25rem;
+}
+
+.navbar__link {
+  padding: 0.5rem 1.25rem;
+  border-radius: var(--radius-lg);
+  text-decoration: none;
+  font-size: 1.425rem;
+  font-weight: 200;
+  color: var(--color-text-subtle);
+  background-color: transparent;
+  transition: all 0.15s ease;
+}
+
+.navbar__link--active {
+  font-weight: 600;
+  color: var(--color-text);
+  background-color: var(--color-bg-card);
+}
+
+.navbar__user {
+  font-size: 1.275rem;
+  color: #777;
+}
+
+.navbar__logout {
+  padding: 0.4rem 1rem;
+  font-size: 1.275rem;
+  font-weight: 400;
+  background-color: transparent;
+  color: var(--color-text-subtle);
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-lg);
+  cursor: pointer;
+  transition: all 0.15s ease;
+}

frontend/src/components/Navbar.jsx

@@ -1,10 +1,11 @@
 import { Link, useLocation } from "react-router-dom";
 import { useAuth } from "../contexts/AuthContext";
+import "./Navbar.css";
 
 const navLinks = [
   { to: "/addresses", label: "Addresses" },
   { to: "/alerts", label: "Configure Alerts" },
-  { to: "/history", label: "Alert History" },
+  { to: "/alertevents", label: "Alert Events" },
 ];
 
 export default function Navbar() {
@@ -14,43 +15,17 @@ export default function Navbar() {
   if (!currentUser) return null;
 
   return (
-    <nav style={{
-      display: "flex",
-      justifyContent: "space-between",
-      alignItems: "center",
-      padding: "1rem 2rem",
-      marginBottom: "1.5rem",
-      backgroundColor: "#1a1a1a",
-      borderBottom: "1px solid #333",
-    }}>
-      <div style={{ display: "flex", alignItems: "center", gap: "0.5rem" }}>
-        <span style={{
-          fontWeight: 700,
-          fontSize: "1.1rem",
-          color: "#fff",
-          marginRight: "2rem",
-          letterSpacing: "0.5px",
-        }}>
-          Koin Ping
-        </span>
-
-        <div style={{ display: "flex", gap: "0.25rem" }}>
+    <nav className="navbar">
+      <div className="flex flex--center gap-sm">
+        <span className="navbar__brand">Koin Ping</span>
+        <div className="navbar__links">
           {navLinks.map(({ to, label }) => {
             const isActive = location.pathname === to;
             return (
               <Link
                 key={to}
                 to={to}
-                style={{
-                  padding: "0.5rem 1.25rem",
-                  borderRadius: "6px",
-                  textDecoration: "none",
-                  fontSize: "1.425rem",
-                  fontWeight: isActive ? 600 : 200,
-                  color: isActive ? "#fff" : "#999",
-                  backgroundColor: isActive ? "#333" : "transparent",
-                  transition: "all 0.15s ease",
-                }}
+                className={`navbar__link ${isActive ? "navbar__link--active" : ""}`}
               >
                 {label}
               </Link>
@@ -59,24 +34,9 @@ export default function Navbar() {
         </div>
       </div>
 
-      <div style={{ display: "flex", alignItems: "center", gap: "1.25rem" }}>
-        <span style={{ fontSize: "1.275rem", color: "#777" }}>
-          {currentUser.email}
-        </span>
-        <button
-          onClick={logout}
-          style={{
-            padding: "0.4rem 1rem",
-            fontSize: "1.275rem",
-            fontWeight: 400,
-            backgroundColor: "transparent",
-            color: "#999",
-            border: "1px solid #444",
-            borderRadius: "6px",
-            cursor: "pointer",
-            transition: "all 0.15s ease",
-          }}
-        >
+      <div className="flex flex--center gap-lg">
+        <span className="navbar__user">{currentUser.email}</span>
+        <button onClick={logout} className="navbar__logout">
           Logout
         </button>
       </div>

frontend/src/index.css

@@ -1,5 +1,43 @@
 @import url('https://fonts.googleapis.com/css2?family=Nunito:ital,wght@0,200..1000;1,200..1000&display=swap');
 
+:root {
+  --color-primary: #0066cc;
+  --color-primary-hover: #0077ee;
+  --color-brand: #e62525;
+  --color-success: #28a745;
+  --color-success-text: #00ff00;
+  --color-success-bg: #00ff0020;
+  --color-success-border: #00ff00;
+  --color-error: #ff6666;
+  --color-error-bg: #ff000020;
+  --color-error-border: #ff0000;
+  --color-warning: #ffcc44;
+  --color-warning-bg: #3a2e00;
+  --color-warning-border: #aa7700;
+  --color-danger: #cc6666;
+  --color-danger-border: #884444;
+
+  --color-bg: #1a1a1a;
+  --color-bg-elevated: #242424;
+  --color-bg-card: #333;
+  --color-bg-section: #2a2a2a;
+
+  --color-border: #444;
+  --color-border-light: #333;
+  --color-border-section: #3a3a3a;
+
+  --color-text: white;
+  --color-text-muted: #b3b3b3;
+  --color-text-dimmed: #808080;
+  --color-text-subtle: #999;
+  --color-text-label: #ccc;
+
+  --radius-sm: 3px;
+  --radius-md: 4px;
+  --radius-lg: 6px;
+  --radius-xl: 8px;
+}
+
 *,
 *::before,
 *::after {
@@ -21,13 +59,300 @@ body {
   -moz-osx-font-smoothing: grayscale;
 }
 
-h1, h2, h3, h4, h5, h6 {
+h1,
+h2,
+h3,
+h4,
+h5,
+h6 {
   font-family: 'Nunito', sans-serif;
   font-weight: 200;
 }
 
-input, select, textarea, button {
+input,
+select,
+textarea,
+button {
   font-family: 'Nunito', sans-serif;
   font-size: 1rem;
   font-weight: 200;
 }
+
+/* ── Page Layouts ─────────────────────────────────────────── */
+
+.page {
+  max-width: 800px;
+  margin: 0 auto;
+  padding: 2rem;
+}
+
+.page--wide {
+  max-width: 1400px;
+}
+
+/* ── Cards & Sections ─────────────────────────────────────── */
+
+.card {
+  padding: 1rem;
+  background-color: var(--color-bg-card);
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-md);
+}
+
+.section {
+  margin-bottom: 1.5rem;
+  padding: 1rem;
+  background-color: var(--color-bg-section);
+  border-radius: var(--radius-lg);
+  border: 1px solid var(--color-border-section);
+}
+
+/* ── Form Controls ────────────────────────────────────────── */
+
+.form-field {
+  margin-bottom: 1.25rem;
+}
+
+.form-field--last {
+  margin-bottom: 1.75rem;
+}
+
+.form-label {
+  display: block;
+  margin-bottom: 0.25rem;
+  font-size: 0.9rem;
+  color: var(--color-text-label);
+}
+
+.form-control {
+  width: 100%;
+  padding: 0.5rem;
+  font-size: 1rem;
+  background-color: var(--color-bg-elevated);
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-md);
+  color: var(--color-text);
+}
+
+.form-control:focus {
+  outline: none;
+  border-color: var(--color-primary);
+  box-shadow: 0 0 0 2px rgba(0, 102, 204, 0.25);
+}
+
+.form-control--mono {
+  font-family: monospace;
+}
+
+.form-select {
+  width: 100%;
+  padding: 0.5rem;
+  font-size: 1rem;
+  background-color: var(--color-bg);
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-md);
+  color: var(--color-text);
+}
+
+/* ── Buttons ──────────────────────────────────────────────── */
+
+.btn {
+  padding: 0.5rem 1rem;
+  font-size: 1rem;
+  border: none;
+  border-radius: var(--radius-md);
+  cursor: pointer;
+  color: var(--color-text);
+  transition: opacity 0.15s ease;
+}
+
+.btn:disabled {
+  opacity: 0.6;
+  cursor: not-allowed;
+}
+
+.btn--primary {
+  background-color: var(--color-primary);
+}
+
+.btn--success {
+  background-color: var(--color-success);
+}
+
+.btn--secondary {
+  background-color: #6c757d;
+}
+
+.btn--danger {
+  background-color: transparent;
+  border: 1px solid var(--color-danger-border);
+  color: var(--color-danger);
+}
+
+.btn--ghost {
+  background-color: transparent;
+  border: 1px solid var(--color-border);
+  color: var(--color-text-subtle);
+}
+
+.btn--sm {
+  padding: 0.25rem 0.6rem;
+  font-size: 0.85rem;
+}
+
+.btn--lg {
+  padding: 0.75rem 1.5rem;
+}
+
+/* ── Feedback Alerts ──────────────────────────────────────── */
+
+.alert {
+  padding: 0.75rem;
+  margin-bottom: 1rem;
+  border-radius: var(--radius-md);
+}
+
+.alert--error {
+  background-color: var(--color-error-bg);
+  border: 1px solid var(--color-error-border);
+  color: var(--color-error);
+}
+
+.alert--success {
+  background-color: var(--color-success-bg);
+  border: 1px solid var(--color-success-border);
+  color: var(--color-success-text);
+}
+
+.alert--warning {
+  background-color: var(--color-warning-bg);
+  border: 1px solid var(--color-warning-border);
+  color: var(--color-warning);
+}
+
+/* ── Lists ────────────────────────────────────────────────── */
+
+.list-unstyled {
+  list-style: none;
+  padding: 0;
+}
+
+.list-item--card {
+  padding: 1rem;
+  margin-bottom: 0.5rem;
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-md);
+  background-color: var(--color-bg-card);
+}
+
+/* ── Typography Helpers ───────────────────────────────────── */
+
+.text-muted {
+  color: var(--color-text-muted);
+}
+
+.text-dimmed {
+  color: var(--color-text-dimmed);
+}
+
+.text-mono {
+  font-family: monospace;
+}
+
+.text-bold {
+  font-weight: bold;
+}
+
+.text-error {
+  color: red;
+}
+
+.text-sm {
+  font-size: 1.035rem;
+}
+
+.text-xs {
+  font-size: 0.978rem;
+}
+
+.help-link {
+  color: var(--color-primary);
+  font-size: 0.85rem;
+}
+
+/* ── Flex Utilities ───────────────────────────────────────── */
+
+.flex {
+  display: flex;
+}
+
+.flex--between {
+  justify-content: space-between;
+}
+
+.flex--center {
+  align-items: center;
+}
+
+.flex--column {
+  flex-direction: column;
+}
+
+.flex--wrap {
+  flex-wrap: wrap;
+}
+
+.gap-xs {
+  gap: 0.25rem;
+}
+
+.gap-sm {
+  gap: 0.5rem;
+}
+
+.gap-md {
+  gap: 0.75rem;
+}
+
+.gap-lg {
+  gap: 1rem;
+}
+
+/* ── Spacing Helpers ──────────────────────────────────────── */
+
+.mb-0 {
+  margin-bottom: 0;
+}
+
+.mb-sm {
+  margin-bottom: 0.5rem;
+}
+
+.mb-md {
+  margin-bottom: 1rem;
+}
+
+.mb-lg {
+  margin-bottom: 1.5rem;
+}
+
+.mb-xl {
+  margin-bottom: 2rem;
+}
+
+.mt-0 {
+  margin-top: 0;
+}
+
+.mt-md {
+  margin-top: 1rem;
+}
+
+.text-white {
+  color: white;
+}
+
+.text-white-sm {
+  color: white;
+  font-size: 0.85rem;
+}

frontend/src/pages/Addresses.css

@@ -0,0 +1,30 @@
+.address__edit-input {
+  background: var(--color-border);
+  border: 1px solid #666;
+  border-radius: var(--radius-sm);
+  color: var(--color-text);
+  padding: 0.25rem 0.5rem;
+  font-size: 0.9rem;
+}
+
+.address__edit-link {
+  cursor: pointer;
+  background: transparent;
+  border: none;
+  color: #6699cc;
+  font-size: 0.8rem;
+  padding: 0;
+  text-decoration: underline;
+}
+
+.address__remove {
+  cursor: pointer;
+  background: transparent;
+  border: 1px solid var(--color-danger-border);
+  color: var(--color-danger);
+  border-radius: var(--radius-sm);
+  padding: 0.3rem 0.7rem;
+  font-size: 0.85rem;
+  margin-left: 1rem;
+  flex-shrink: 0;
+}

frontend/src/pages/Addresses.jsx

@@ -1,13 +1,15 @@
 import { useState, useEffect } from "react";
 import AddressForm from "../components/AddressForm";
-import { getAddresses, createAddress } from "../api/addresses";
+import { getAddresses, createAddress, deleteAddress, updateAddress } from "../api/addresses";
+import "./Addresses.css";
 
 export default function Addresses() {
     const [addresses, setAddresses] = useState([]);
     const [loading, setLoading] = useState(true);
     const [error, setError] = useState(null);
+    const [editingId, setEditingId] = useState(null);
+    const [editLabel, setEditLabel] = useState("");
 
-    // Load addresses on mount
     useEffect(() => {
         async function fetchAddresses() {
             try {
@@ -25,66 +27,128 @@ export default function Addresses() {
         fetchAddresses();
     }, []);
 
-    // Handle new address submission
     async function handleAddressSubmit(data) {
         try {
             const newAddress = await createAddress(data);
-            // Append new address to state
             setAddresses((prev) => [...prev, newAddress]);
-            setError(null); // Clear any previous errors
+            setError(null);
         } catch (err) {
             setError(err.message);
             console.error("Failed to create address:", err);
         }
     }
 
-    return (
-        <div style={{ maxWidth: "800px", margin: "0 auto", padding: "2rem" }}>
-            <h1>Tracked Addresses</h1>
+    async function handleDelete(id, label) {
+        const displayName = label || "this address";
+        if (!window.confirm(`Remove "${displayName}"? This will also delete all associated alert rules.`)) {
+            return;
+        }
+        try {
+            await deleteAddress(id);
+            setAddresses((prev) => prev.filter((a) => a.id !== id));
+            setError(null);
+        } catch (err) {
+            setError(err.message);
+            console.error("Failed to delete address:", err);
+        }
+    }
 
-            <div style={{ marginBottom: "2rem" }}>
+    function handleEditStart(addr) {
+        setEditingId(addr.id);
+        setEditLabel(addr.label ?? "");
+    }
+
+    async function handleEditSave(id) {
+        try {
+            const updated = await updateAddress(id, { label: editLabel || null });
+            setAddresses((prev) => prev.map((a) => (a.id === id ? updated : a)));
+            setEditingId(null);
+            setEditLabel("");
+            setError(null);
+        } catch (err) {
+            setError(err.message);
+            console.error("Failed to update address:", err);
+        }
+    }
+
+    function handleEditCancel() {
+        setEditingId(null);
+        setEditLabel("");
+    }
+
+    return (
+        <div className="page">
+            <h1>Add Addresses to Track</h1>
+
+            <div className="mb-xl">
                 <AddressForm onSubmit={handleAddressSubmit} />
             </div>
 
             <div>
-                <h2>Existing Addresses</h2>
+                <h2>Existing Tracked Addresses</h2>
                 {loading && <p>Loading addresses...</p>}
-                {error && <p style={{ color: "red" }}>Error: {error}</p>}
+                {error && <p className="text-error">Error: {error}</p>}
                 {!loading && !error && addresses.length === 0 && (
-                    <p style={{ color: "#808080" }}>
+                    <p className="text-dimmed">
                         No addresses tracked yet. Add one above to get started.
                     </p>
                 )}
                 {addresses.length > 0 && (
-                    <ul style={{ listStyle: "none", padding: 0 }}>
+                    <ul className="list-unstyled">
                         {addresses.map((addr, index) => (
-                            <li
-                                key={addr.id || index}
-                                style={{
-                                    padding: "1rem",
-                                    marginBottom: "0.5rem",
-                                    border: "1px solid #444",
-                                    borderRadius: "4px",
-                                    backgroundColor: "#333",
+                            <li key={addr.id || index} className="list-item--card">
+                                <div className="flex flex--between flex--center">
+                                    <div>
+                                        {editingId === addr.id ? (
+                                            <div className="flex flex--center gap-sm mb-sm">
+                                                <input
+                                                    value={editLabel}
+                                                    onChange={(e) => setEditLabel(e.target.value)}
+                                                    placeholder="Label (optional)"
+                                                    className="address__edit-input"
+                                                    onKeyDown={(e) => {
+                                                        if (e.key === "Enter") handleEditSave(addr.id);
+                                                        if (e.key === "Escape") handleEditCancel();
                                                     }}
+                                                    autoFocus
+                                                />
+                                                <button
+                                                    onClick={() => handleEditSave(addr.id)}
+                                                    className="btn btn--primary btn--sm"
                                                 >
-                                <div
-                                    style={{
-                                        fontWeight: "bold",
-                                        marginBottom: "0.25rem",
-                                    }}
+                                                    Save
+                                                </button>
+                                                <button
+                                                    onClick={handleEditCancel}
+                                                    className="btn btn--ghost btn--sm"
                                                 >
-                                    {addr.label || "Unlabeled"}
+                                                    Cancel
+                                                </button>
                                             </div>
-                                <div
-                                    style={{
-                                        fontFamily: "monospace",
-                                        fontSize: "1.035rem",
-                                        color: "#b3b3b3",
-                                    }}
+                                        ) : (
+                                            <div className="flex flex--center gap-sm mb-sm">
+                                                <span className="text-bold">
+                                                    {addr.label || "Unlabeled"}
+                                                </span>
+                                                <button
+                                                    onClick={() => handleEditStart(addr)}
+                                                    className="address__edit-link"
                                                 >
+                                                    Edit
+                                                </button>
+                                            </div>
+                                        )}
+                                        <div className="text-mono text-sm text-muted">
                                             {addr.address}
                                         </div>
+                                    </div>
+                                    <button
+                                        onClick={() => handleDelete(addr.id, addr.label)}
+                                        className="address__remove"
+                                    >
+                                        Remove
+                                    </button>
+                                </div>
                             </li>
                         ))}
                     </ul>

frontend/src/pages/AlertHistory.css

@@ -0,0 +1,7 @@
+.alert-history__item {
+  padding: 1rem;
+  margin-bottom: 0.75rem;
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-md);
+  background-color: var(--color-bg-card);
+}

frontend/src/pages/AlertHistory.jsx

@@ -1,12 +1,12 @@
 import { useState, useEffect } from "react";
 import { getAlertEvents } from "../api/alertEvents";
+import "./AlertHistory.css";
 
 export default function AlertHistory() {
     const [alertEvents, setAlertEvents] = useState([]);
     const [loading, setLoading] = useState(true);
     const [error, setError] = useState(null);
 
-    // Fetch alert events on mount
     useEffect(() => {
         async function fetchAlertEvents() {
             try {
@@ -25,49 +25,32 @@ export default function AlertHistory() {
     }, []);
 
     if (loading) {
-        return <div style={{ padding: "2rem" }}>Loading...</div>;
+        return <div className="page">Loading...</div>;
     }
 
     if (error) {
         return (
-            <div style={{ padding: "2rem", color: "red" }}>Error: {error}</div>
+            <div className="page text-error">Error: {error}</div>
         );
     }
 
     return (
-        <div style={{ maxWidth: "800px", margin: "0 auto", padding: "2rem" }}>
-            <h1>Recent Alerts</h1>
+        <div className="page">
+            <h1>Recent Alert Events</h1>
 
             {alertEvents.length === 0 ? (
-                <p style={{ color: "#808080" }}>No alerts yet</p>
+                <p className="text-dimmed">No alerts yet</p>
             ) : (
-                <ul style={{ listStyle: "none", padding: 0 }}>
+                <ul className="list-unstyled">
                     {alertEvents.map((event) => (
-                        <li
-                            key={event.id}
-                            style={{
-                                padding: "1rem",
-                                marginBottom: "0.75rem",
-                                border: "1px solid #444",
-                                borderRadius: "4px",
-                                backgroundColor: "#333",
-                            }}
-                        >
-                            <div style={{ marginBottom: "0.5rem" }}>
-                                {event.message}
-                            </div>
+                        <li key={event.id} className="alert-history__item">
+                            <div className="mb-sm">{event.message}</div>
                             {event.address_label && (
-                                <div
-                                    style={{
-                                    fontSize: "1.035rem",
-                                    color: "#808080",
-                                        marginBottom: "0.25rem",
-                                    }}
-                                >
+                                <div className="text-sm text-dimmed">
                                     Address: {event.address_label}
                                 </div>
                             )}
-                            <small style={{ color: "#b3b3b3" }}>
+                            <small className="text-muted">
                                 {formatTimestamp(event.timestamp)}
                             </small>
                         </li>
@@ -78,7 +61,6 @@ export default function AlertHistory() {
     );
 }
 
-// Helper to format timestamp for display
 function formatTimestamp(timestamp) {
     const date = new Date(timestamp);
     return date.toLocaleString();

frontend/src/pages/Alerts.css

@@ -0,0 +1,63 @@
+.alerts-grid {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 2rem;
+  align-items: start;
+}
+
+.alerts__address-info {
+  padding: 1rem;
+  margin-bottom: 2rem;
+  background-color: var(--color-bg-card);
+  border-radius: var(--radius-md);
+  border: 1px solid var(--color-border);
+}
+
+.alerts__toggle-panel {
+  margin-bottom: 1.5rem;
+  padding: 1rem;
+  background-color: var(--color-bg-card);
+  border-radius: var(--radius-md);
+}
+
+.alerts__toggle-label {
+  display: flex;
+  align-items: center;
+  cursor: pointer;
+}
+
+.alerts__toggle-checkbox {
+  margin-right: 0.5rem;
+  width: 18px;
+  height: 18px;
+}
+
+.alerts__toggle-hint {
+  font-size: 0.978rem;
+  color: var(--color-text-dimmed);
+  margin-top: 0.5rem;
+  margin-left: 26px;
+}
+
+.alerts__rule {
+  padding: 1rem;
+  margin-bottom: 0.5rem;
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-md);
+  background-color: var(--color-bg-card);
+}
+
+.alerts__rule--disabled {
+  opacity: 0.6;
+}
+
+.alerts__email-buttons {
+  display: flex;
+  gap: 0.5rem;
+}
+
+.alerts__save-test {
+  display: flex;
+  gap: 0.75rem;
+  margin-top: 1rem;
+}

frontend/src/pages/Alerts.jsx

@@ -1,6 +1,7 @@
 import { useState, useEffect } from "react";
 import AlertForm from "../components/AlertForm";
 import Button from "../components/Button";
+import Input from "../components/Input";
 import { getAddresses } from "../api/addresses";
 import {
     getAlerts,
@@ -15,35 +16,7 @@ import {
     setupEmail,
     sendEmailDigest,
 } from "../api/notificationConfig";
-
-const inputStyle = {
-    width: "100%",
-    padding: "0.5rem",
-    fontSize: "0.9rem",
-    backgroundColor: "#1a1a1a",
-    border: "1px solid #444",
-    borderRadius: "4px",
-    color: "white",
-    fontFamily: "monospace",
-    boxSizing: "border-box",
-};
-
-const labelStyle = {
-    display: "block",
-    marginBottom: "0.25rem",
-    fontSize: "0.9rem",
-    color: "#ccc",
-};
-
-const helpLinkStyle = { color: "#0066cc", fontSize: "0.85rem" };
-
-const sectionStyle = {
-    marginBottom: "1.5rem",
-    padding: "1rem",
-    backgroundColor: "#2a2a2a",
-    borderRadius: "6px",
-    border: "1px solid #3a3a3a",
-};
+import "./Alerts.css";
 
 export default function Alerts() {
     const [addresses, setAddresses] = useState([]);
@@ -52,7 +25,6 @@ export default function Alerts() {
     const [loading, setLoading] = useState(true);
     const [error, setError] = useState(null);
 
-    // Notification config state
     const [notificationEnabled, setNotificationEnabled] = useState(false);
     const [discordWebhookUrl, setDiscordWebhookUrl] = useState("");
     const [telegramBotToken, setTelegramBotToken] = useState("");
@@ -273,42 +245,28 @@ export default function Alerts() {
     const selectedAddress = addresses.find((a) => a.id === selectedAddressId);
 
     if (loading) {
-        return <div style={{ padding: "2rem" }}>Loading addresses...</div>;
+        return <div className="page">Loading addresses...</div>;
     }
 
     if (addresses.length === 0) {
         return (
-            <div style={{ padding: "2rem" }}>
-                <p>
-                    No addresses tracked yet. Add an address first to create
-                    alerts.
-                </p>
+            <div className="page">
+                <p>No addresses tracked yet. Add an address first to create alerts.</p>
             </div>
         );
     }
 
     return (
-        <div style={{ maxWidth: "1400px", margin: "0 auto", padding: "2rem" }}>
-            <h1 style={{ marginBottom: "2rem" }}>
-                Alert Rules & Notifications
-            </h1>
+        <div className="page page--wide">
+            <h1 className="mb-xl">Alert Rules & Notifications</h1>
 
-            <div
-                style={{
-                    display: "grid",
-                    gridTemplateColumns: "1fr 1fr",
-                    gap: "2rem",
-                    alignItems: "start",
-                }}
-            >
+            <div className="alerts-grid">
                 {/* LEFT COLUMN: Alert Rules */}
                 <div>
-                    <h2 style={{ marginTop: 0 }}>Alert Rules</h2>
+                    <h2 className="mt-0">Alert Rules</h2>
 
-                    <div style={{ marginBottom: "2rem" }}>
-                        <label
-                            style={{ display: "block", marginBottom: "0.5rem" }}
-                        >
+                    <div className="mb-xl">
+                        <label className="form-label mb-sm">
                             <strong>Select Address:</strong>
                         </label>
                         <select
@@ -316,15 +274,7 @@ export default function Alerts() {
                             onChange={(e) =>
                                 setSelectedAddressId(Number(e.target.value))
                             }
-                            style={{
-                                width: "100%",
-                                padding: "0.5rem",
-                                fontSize: "1rem",
-                                backgroundColor: "#1a1a1a",
-                                border: "1px solid #444",
-                                borderRadius: "4px",
-                                color: "white",
-                            }}
+                            className="form-select"
                         >
                             {addresses.map((addr) => (
                                 <option key={addr.id} value={addr.id}>
@@ -336,43 +286,19 @@ export default function Alerts() {
 
                     {selectedAddress && (
                         <>
-                            <div
-                                style={{
-                                    padding: "1rem",
-                                    marginBottom: "2rem",
-                                    backgroundColor: "#333",
-                                    borderRadius: "4px",
-                                    border: "1px solid #444",
-                                }}
-                            >
-                                <div
-                                    style={{
-                                        fontSize: "1.035rem",
-                                        color: "#b3b3b3",
-                                    }}
-                                >
+                            <div className="alerts__address-info">
+                                <div className="text-sm text-muted">
                                     Managing alerts for:
                                 </div>
-                                <div
-                                    style={{
-                                        fontWeight: "bold",
-                                        marginTop: "0.25rem",
-                                    }}
-                                >
+                                <div className="text-bold">
                                     {selectedAddress.label || "Unlabeled"}
                                 </div>
-                                <div
-                                    style={{
-                                        fontFamily: "monospace",
-                                        fontSize: "1.035rem",
-                                        color: "#b3b3b3",
-                                    }}
-                                >
+                                <div className="text-mono text-sm text-muted">
                                     {selectedAddress.address}
                                 </div>
                             </div>
 
-                            <div style={{ marginBottom: "2rem" }}>
+                            <div className="mb-xl">
                                 <h3>Create New Alert</h3>
                                 <AlertForm onSubmit={handleAlertSubmit} />
                             </div>
@@ -380,112 +306,43 @@ export default function Alerts() {
                             <div>
                                 <h3>Active Alert Rules</h3>
                                 {error && (
-                                    <p style={{ color: "red" }}>
-                                        Error: {error}
-                                    </p>
+                                    <p className="text-error">Error: {error}</p>
                                 )}
                                 {alerts.length === 0 ? (
-                                    <p style={{ color: "#666" }}>
-                                        No alert rules defined yet. Create one
-                                        above.
+                                    <p className="text-dimmed">
+                                        No alert rules defined yet. Create one above.
                                     </p>
                                 ) : (
-                                    <ul
-                                        style={{
-                                            listStyle: "none",
-                                            padding: 0,
-                                        }}
-                                    >
+                                    <ul className="list-unstyled">
                                         {alerts.map((alert) => (
                                             <li
                                                 key={alert.id}
-                                                style={{
-                                                    padding: "1rem",
-                                                    marginBottom: "0.5rem",
-                                                    border: "1px solid #444",
-                                                    borderRadius: "4px",
-                                                    backgroundColor: "#333",
-                                                    opacity: alert.enabled
-                                                        ? 1
-                                                        : 0.6,
-                                                }}
+                                                className={`alerts__rule ${!alert.enabled ? "alerts__rule--disabled" : ""}`}
                                             >
-                                                <div
-                                                    style={{
-                                                        display: "flex",
-                                                        justifyContent:
-                                                            "space-between",
-                                                        alignItems:
-                                                            "flex-start",
-                                                    }}
-                                                >
-                                                    <div style={{ flex: 1 }}>
-                                                        <div
-                                                            style={{
-                                                                fontWeight:
-                                                                    "bold",
-                                                                marginBottom:
-                                                                    "0.25rem",
-                                                            }}
-                                                        >
-                                                            {formatAlertType(
-                                                                alert.type,
-                                                            )}
+                                                <div className="flex flex--between">
+                                                    <div>
+                                                        <div className="text-bold mb-sm">
+                                                            {formatAlertType(alert.type)}
                                                         </div>
                                                         {alert.threshold && (
-                                                            <div
-                                                                style={{
-                                                                    fontSize:
-                                                                        "1.035rem",
-                                                                    color: "#b3b3b3",
-                                                                }}
-                                                            >
-                                                                Threshold:{" "}
-                                                                {
-                                                                    alert.threshold
-                                                                }{" "}
-                                                                ETH
+                                                            <div className="text-sm text-muted">
+                                                                Threshold: {alert.threshold} ETH
                                                             </div>
                                                         )}
-                                                        <div
-                                                            style={{
-                                                                fontSize:
-                                                                    "0.978rem",
-                                                                color: "#808080",
-                                                                marginTop:
-                                                                    "0.25rem",
-                                                            }}
-                                                        >
-                                                            Status:{" "}
-                                                            {alert.enabled
-                                                                ? "Enabled"
-                                                                : "Disabled"}
+                                                        <div className="text-xs text-dimmed">
+                                                            Status: {alert.enabled ? "Enabled" : "Disabled"}
                                                         </div>
                                                     </div>
-                                                    <div
-                                                        style={{
-                                                            display: "flex",
-                                                            gap: "0.5rem",
-                                                        }}
-                                                    >
+                                                    <div className="flex flex--center gap-sm">
                                                         <Button
                                                             onClick={() =>
-                                                                handleToggleAlert(
-                                                                    alert.id,
-                                                                    alert.enabled,
-                                                                )
+                                                                handleToggleAlert(alert.id, alert.enabled)
                                                             }
                                                         >
-                                                            {alert.enabled
-                                                                ? "Disable"
-                                                                : "Enable"}
+                                                            {alert.enabled ? "Disable" : "Enable"}
                                                         </Button>
                                                         <Button
-                                                            onClick={() =>
-                                                                handleDeleteAlert(
-                                                                    alert.id,
-                                                                )
-                                                            }
+                                                            onClick={() => handleDeleteAlert(alert.id)}
                                                         >
                                                             Delete
                                                         </Button>
@@ -502,329 +359,152 @@ export default function Alerts() {
 
                 {/* RIGHT COLUMN: Notification Settings */}
                 <div>
-                    <h2 style={{ marginTop: 0 }}>Notification Settings</h2>
+                    <h2 className="mt-0">Notification Settings</h2>
 
                     {notificationSuccess && (
-                        <div
-                            style={{
-                                padding: "0.75rem",
-                                marginBottom: "1rem",
-                                backgroundColor: "#00ff0020",
-                                border: "1px solid #00ff00",
-                                borderRadius: "4px",
-                                color: "#00ff00",
-                            }}
-                        >
-                            {notificationSuccess}
-                        </div>
+                        <div className="alert alert--success">{notificationSuccess}</div>
                     )}
 
                     {notificationError && (
-                        <div
-                            style={{
-                                padding: "0.75rem",
-                                marginBottom: "1rem",
-                                backgroundColor: "#ff000020",
-                                border: "1px solid #ff0000",
-                                borderRadius: "4px",
-                                color: "#ff6666",
-                            }}
-                        >
-                            {notificationError}
-                        </div>
+                        <div className="alert alert--error">{notificationError}</div>
                     )}
 
                     {/* Master toggle */}
-                    <div
-                        style={{
-                            marginBottom: "1.5rem",
-                            padding: "1rem",
-                            backgroundColor: "#333",
-                            borderRadius: "4px",
-                        }}
-                    >
-                        <label
-                            style={{
-                                display: "flex",
-                                alignItems: "center",
-                                cursor: "pointer",
-                            }}
-                        >
+                    <div className="alerts__toggle-panel">
+                        <label className="alerts__toggle-label">
                             <input
                                 type="checkbox"
                                 checked={notificationEnabled}
                                 onChange={(e) =>
                                     setNotificationEnabled(e.target.checked)
                                 }
-                                style={{
-                                    marginRight: "0.5rem",
-                                    width: "18px",
-                                    height: "18px",
-                                }}
+                                className="alerts__toggle-checkbox"
                             />
-                            <span style={{ fontWeight: "bold" }}>
-                                Enable Notifications
-                            </span>
+                            <span className="text-bold">Enable Notifications</span>
                         </label>
-                        <div
-                            style={{
-                                fontSize: "0.978rem",
-                                color: "#808080",
-                                marginTop: "0.5rem",
-                                marginLeft: "26px",
-                            }}
-                        >
+                        <div className="alerts__toggle-hint">
                             Master switch for all notification channels
                         </div>
                     </div>
 
-                    {/* All channel settings — hidden when master toggle is off */}
-                    <div
-                        style={{
-                            display: notificationEnabled ? "block" : "none",
-                        }}
-                    >
+                    {/* All channel settings -- hidden when master toggle is off */}
+                    {notificationEnabled && (
+                        <>
                             {/* Telegram */}
-                        <div style={sectionStyle}>
-                            <h3 style={{ marginTop: 0, marginBottom: "1rem" }}>
-                                Telegram
-                            </h3>
-
-                            <div style={{ marginBottom: "0.75rem" }}>
-                                <label style={labelStyle}>Bot Token</label>
-                                <input
-                                    type="text"
+                            <div className="section">
+                                <h3 className="mt-0 mb-md">Telegram</h3>
+                                <Input
+                                    label="Bot Token"
                                     value={telegramBotToken}
-                                    onChange={(e) =>
-                                        setTelegramBotToken(e.target.value)
-                                    }
+                                    onChange={setTelegramBotToken}
                                     placeholder="123456789:ABCdefGHIjklMNOpqrSTUvwxYZ"
-                                    style={inputStyle}
                                 />
-                            </div>
-
-                            <div style={{ marginBottom: "0.5rem" }}>
-                                <label style={labelStyle}>Chat ID</label>
-                                <input
-                                    type="text"
+                                <Input
+                                    label="Chat ID"
                                     value={telegramChatId}
-                                    onChange={(e) =>
-                                        setTelegramChatId(e.target.value)
-                                    }
+                                    onChange={setTelegramChatId}
                                     placeholder="-1001234567890"
-                                    style={inputStyle}
                                 />
-                            </div>
-
                                 <a
                                     href="https://core.telegram.org/bots#how-do-i-create-a-bot"
                                     target="_blank"
                                     rel="noopener noreferrer"
-                                style={helpLinkStyle}
+                                    className="help-link"
                                 >
                                     How to create a Telegram bot & get your Chat ID
                                 </a>
                             </div>
 
                             {/* Email */}
-                        <div style={sectionStyle}>
-                            <h3 style={{ marginTop: 0, marginBottom: "1rem" }}>
-                                Email
-                            </h3>
-
-                            <div style={{ marginBottom: "0.75rem" }}>
-                                <label style={labelStyle}>Email Address</label>
-                                <input
+                            <div className="section">
+                                <h3 className="mt-0 mb-md">Email</h3>
+                                <Input
+                                    label="Email Address"
                                     type="email"
                                     value={email}
-                                    onChange={(e) => setEmail(e.target.value)}
+                                    onChange={setEmail}
                                     placeholder="you@example.com"
-                                    style={inputStyle}
                                 />
+                                <div className="help-link text-dimmed mb-md">
+                                    Alert notifications and digests will be sent to this address
                                 </div>
-
-                            <div
-                                style={{
-                                    fontSize: "0.85rem",
-                                    color: "#808080",
-                                    marginBottom: "0.75rem",
-                                }}
-                            >
-                                Alert notifications and digests will be sent to
-                                this address
-                            </div>
-
-                            <div
-                                style={{
-                                    display: "flex",
-                                    gap: "0.5rem",
-                                }}
-                            >
-                                <button
+                                <div className="alerts__email-buttons">
+                                    <Button
                                         onClick={handleSetupEmail}
                                         disabled={settingUpEmail || !email}
-                                    style={{
-                                        padding: "0.5rem 1rem",
-                                        fontSize: "0.85rem",
-                                        backgroundColor:
-                                            settingUpEmail || !email
-                                                ? "#333"
-                                                : "#0066cc",
-                                        color: "white",
-                                        border: "none",
-                                        borderRadius: "4px",
-                                        cursor:
-                                            settingUpEmail || !email
-                                                ? "not-allowed"
-                                                : "pointer",
-                                    }}
+                                        className="btn--sm"
                                     >
-                                    {settingUpEmail
-                                        ? "Setting up..."
-                                        : "Verify Email"}
-                                </button>
-
-                                <button
+                                        {settingUpEmail ? "Setting up..." : "Verify Email"}
+                                    </Button>
+                                    <Button
                                         onClick={handleSendDigest}
                                         disabled={sendingDigest || !email}
-                                    style={{
-                                        padding: "0.5rem 1rem",
-                                        fontSize: "0.85rem",
-                                        backgroundColor:
-                                            sendingDigest || !email
-                                                ? "#333"
-                                                : "#6c757d",
-                                        color: "white",
-                                        border: "none",
-                                        borderRadius: "4px",
-                                        cursor:
-                                            sendingDigest || !email
-                                                ? "not-allowed"
-                                                : "pointer",
-                                    }}
+                                        variant="secondary"
+                                        className="btn--sm"
                                     >
-                                    {sendingDigest
-                                        ? "Sending..."
-                                        : "Send Digest Now"}
-                                </button>
+                                        {sendingDigest ? "Sending..." : "Send Digest Now"}
+                                    </Button>
                                 </div>
                             </div>
 
                             {/* Discord */}
-                        <div style={sectionStyle}>
-                            <h3 style={{ marginTop: 0, marginBottom: "1rem" }}>
-                                Discord
-                            </h3>
-
-                            <div style={{ marginBottom: "0.5rem" }}>
-                                <label style={labelStyle}>
-                                    Discord Webhook URL
-                                </label>
-                                <input
-                                    type="text"
+                            <div className="section">
+                                <h3 className="mt-0 mb-md">Discord</h3>
+                                <Input
+                                    label="Discord Webhook URL"
                                     value={discordWebhookUrl}
-                                    onChange={(e) =>
-                                        setDiscordWebhookUrl(e.target.value)
-                                    }
+                                    onChange={setDiscordWebhookUrl}
                                     placeholder="https://discord.com/api/webhooks/..."
-                                    style={inputStyle}
                                 />
-                            </div>
-
                                 <a
                                     href="https://support.discord.com/hc/en-us/articles/228383668-Intro-to-Webhooks"
                                     target="_blank"
                                     rel="noopener noreferrer"
-                                style={helpLinkStyle}
+                                    className="help-link"
                                 >
                                     How to get a Discord webhook URL
                                 </a>
                             </div>
 
                             {/* Slack */}
-                        <div style={sectionStyle}>
-                            <h3 style={{ marginTop: 0, marginBottom: "1rem" }}>
-                                Slack
-                            </h3>
-
-                            <div style={{ marginBottom: "0.5rem" }}>
-                                <label style={labelStyle}>
-                                    Slack Webhook URL
-                                </label>
-                                <input
-                                    type="text"
+                            <div className="section">
+                                <h3 className="mt-0 mb-md">Slack</h3>
+                                <Input
+                                    label="Slack Webhook URL"
                                     value={slackWebhookUrl}
-                                    onChange={(e) =>
-                                        setSlackWebhookUrl(e.target.value)
-                                    }
+                                    onChange={setSlackWebhookUrl}
                                     placeholder="https://hooks.slack.com/services/..."
-                                    style={inputStyle}
                                 />
-                            </div>
-
                                 <a
                                     href="https://api.slack.com/messaging/webhooks"
                                     target="_blank"
                                     rel="noopener noreferrer"
-                                style={helpLinkStyle}
+                                    className="help-link"
                                 >
                                     How to set up Slack Incoming Webhooks
                                 </a>
                             </div>
 
-                        {/* Save & Test buttons at the bottom */}
-                        <div
-                            style={{
-                                display: "flex",
-                                gap: "0.75rem",
-                                marginTop: "1rem",
-                            }}
-                        >
-                            <button
+                            {/* Save & Test buttons */}
+                            <div className="alerts__save-test">
+                                <Button
                                     onClick={handleSaveNotificationConfig}
                                     disabled={notificationLoading}
-                                style={{
-                                    padding: "0.75rem 1.5rem",
-                                    fontSize: "1rem",
-                                    backgroundColor: notificationLoading
-                                        ? "#333"
-                                        : "#0066cc",
-                                    color: "white",
-                                    border: "none",
-                                    borderRadius: "4px",
-                                    cursor: notificationLoading
-                                        ? "not-allowed"
-                                        : "pointer",
-                                }}
+                                    className="btn--lg"
                                 >
-                                {notificationLoading
-                                    ? "Saving..."
-                                    : "Save Settings"}
-                            </button>
-
-                            <button
+                                    {notificationLoading ? "Saving..." : "Save Settings"}
+                                </Button>
+                                <Button
                                     onClick={handleTestChannels}
                                     disabled={testingChannels}
-                                style={{
-                                    padding: "0.75rem 1.5rem",
-                                    fontSize: "1rem",
-                                    backgroundColor: testingChannels
-                                        ? "#333"
-                                        : "#28a745",
-                                    color: "white",
-                                    border: "none",
-                                    borderRadius: "4px",
-                                    cursor: testingChannels
-                                        ? "not-allowed"
-                                        : "pointer",
-                                }}
+                                    variant="success"
+                                    className="btn--lg"
                                 >
-                                {testingChannels
-                                    ? "Testing..."
-                                    : "Test All Channels"}
-                            </button>
-                        </div>
+                                    {testingChannels ? "Testing..." : "Test All Channels"}
+                                </Button>
                             </div>
+                        </>
+                    )}
                 </div>
             </div>
         </div>

frontend/src/pages/Login.css

@@ -0,0 +1,64 @@
+.login-page {
+  min-height: 100vh;
+  background-image: url(/ping.png);
+  background-size: 67%;
+  background-position: center;
+  background-repeat: no-repeat;
+}
+
+.login-card {
+  max-width: 400px;
+  margin: 20px auto;
+  padding: 2rem;
+  padding-top: 8rem;
+  border: 1px solid var(--color-border-light);
+  border-radius: var(--radius-xl);
+  background-color: rgba(0, 0, 0, 0.75);
+}
+
+.login-heading {
+  margin-bottom: 2rem;
+  text-align: center;
+  position: relative;
+  top: -20px;
+}
+
+.login-brand {
+  color: var(--color-brand);
+}
+
+.login-button {
+  width: 100%;
+  padding: 0.75rem;
+  font-size: 1.2rem;
+  margin-top: 16px;
+  ;
+}
+
+.login-footer {
+  margin-top: 1.5rem;
+  text-align: center;
+}
+
+.login-signup-link {
+  color: var(--color-primary);
+  text-decoration: none;
+}
+
+@keyframes fadeIn {
+  from {
+    opacity: 0;
+  }
+
+  to {
+    opacity: 1;
+  }
+}
+
+.login-form-hidden {
+  opacity: 0;
+}
+
+.login-form-visible {
+  animation: fadeIn 2s ease-in-out forwards;
+}

frontend/src/pages/Login.jsx

@@ -1,14 +1,11 @@
-/**
- * Login Page
- *
- * Allows existing users to sign in with email and password
- */
-
 import { useState } from "react";
 import { Link, useNavigate } from "react-router-dom";
 import { useAuth } from "../contexts/AuthContext";
+import Input from "../components/Input";
+import "./Login.css";
 
 export default function Login() {
+  const [isVisible, setIsVisible] = useState(false);
   const [email, setEmail] = useState("");
   const [password, setPassword] = useState("");
   const [error, setError] = useState("");
@@ -20,7 +17,6 @@ export default function Login() {
   async function handleSubmit(e) {
     e.preventDefault();
 
-        // Validation
     if (!email || !password) {
       setError("Please fill in all fields");
       return;
@@ -30,7 +26,7 @@ export default function Login() {
       setError("");
       setLoading(true);
       await login(email, password);
-            navigate("/addresses"); // Redirect to main app
+      navigate("/addresses");
     } catch (err) {
       setError("Failed to log in: " + err.message);
     } finally {
@@ -39,108 +35,49 @@ export default function Login() {
   }
 
   return (
-        <div
-            style={{
-                maxWidth: "400px",
-                margin: "4rem auto",
-                padding: "2rem",
-                border: "1px solid #333",
-                borderRadius: "8px",
-            }}
-        >
-            <h1 style={{ marginBottom: "2rem", textAlign: "center" }}>
-                Koin Ping - Login
+    <div className="login-page">
+      <div className="login-card" onMouseEnter={() => setIsVisible(true)}>
+        <h1 className="login-heading">
+          <span className="login-brand">Koin Ping</span> - Login
         </h1>
 
-            {error && (
-                <div
-                    style={{
-                        padding: "0.75rem",
-                        marginBottom: "1rem",
-                        backgroundColor: "#ff000020",
-                        border: "1px solid #ff0000",
-                        borderRadius: "4px",
-                        color: "#ff6666",
-                    }}
-                >
-                    {error}
-                </div>
-            )}
+        <div className={isVisible ? "login-form-visible" : "login-form-hidden"}>
+          {error && <div className="alert alert--error">{error}</div>}
 
           <form onSubmit={handleSubmit}>
-                <div style={{ marginBottom: "1rem" }}>
-                    <label style={{ display: "block", marginBottom: "0.5rem" }}>
-                        Email
-                    </label>
-                    <input
+            <Input
+              label="Email"
               type="email"
               value={email}
-                        onChange={(e) => setEmail(e.target.value)}
+              onChange={setEmail}
               disabled={loading}
-                        style={{
-                            width: "100%",
-                            padding: "0.5rem",
-                            fontSize: "1rem",
-                            backgroundColor: "#242424",
-                            border: "1px solid #444",
-                            borderRadius: "4px",
-                            color: "white",
-                        }}
               required
             />
-                </div>
-
-                <div style={{ marginBottom: "1.5rem" }}>
-                    <label style={{ display: "block", marginBottom: "0.5rem" }}>
-                        Password
-                    </label>
-                    <input
+            <Input
+              label="Password"
               type="password"
               value={password}
-                        onChange={(e) => setPassword(e.target.value)}
+              onChange={setPassword}
               disabled={loading}
-                        style={{
-                            width: "100%",
-                            padding: "0.5rem",
-                            fontSize: "1rem",
-                            backgroundColor: "#242424",
-                            border: "1px solid #444",
-                            borderRadius: "4px",
-                            color: "white",
-                        }}
               required
+              className="form-field--last"
             />
-                </div>
 
-                <button
-                    type="submit"
-                    disabled={loading}
-                    style={{
-                        width: "100%",
-                        padding: "0.75rem",
-                        fontSize: "1rem",
-                        backgroundColor: loading ? "#333" : "#0066cc",
-                        color: "white",
-                        border: "none",
-                        borderRadius: "4px",
-                        cursor: loading ? "not-allowed" : "pointer",
-                    }}
-                >
+            <button type="submit" disabled={loading} className="btn btn--primary login-button">
               {loading ? "Logging in..." : "Log In"}
             </button>
           </form>
 
-            <div style={{ marginTop: "1.5rem", textAlign: "center" }}>
-                <p style={{ color: "#b3b3b3" }}>
+          <div className="login-footer">
+            <p className="text-muted">
               Don't have an account?{" "}
-                    <Link
-                        to="/signup"
-                        style={{ color: "#0066cc", textDecoration: "none" }}
-                    >
+              <Link to="/signup" className="login-signup-link">
                 Sign up here
               </Link>
             </p>
           </div>
         </div>
+      </div>
+    </div>
   );
 }

frontend/src/pages/Onboarding.css

@@ -0,0 +1,238 @@
+.onboarding {
+  min-height: 100vh;
+  background-color: var(--color-bg);
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: flex-start;
+  padding-top: 3rem;
+  padding-bottom: 3rem;
+}
+
+.onboarding__container {
+  width: 100%;
+  max-width: 540px;
+  padding: 0 1rem;
+}
+
+.onboarding__title {
+  text-align: center;
+  margin-bottom: 2rem;
+  color: var(--color-primary);
+  letter-spacing: 0.5px;
+}
+
+.onboarding__card {
+  background-color: var(--color-bg-elevated);
+  border: 1px solid var(--color-border-light);
+  border-radius: var(--radius-xl);
+  padding: 2rem;
+}
+
+.onboarding__login-link {
+  text-align: center;
+  margin-top: 1.25rem;
+  color: #888;
+  font-size: 0.9rem;
+}
+
+.onboarding__login-link a {
+  color: var(--color-primary);
+}
+
+/* Progress bar */
+.progress-bar {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  margin-bottom: 2rem;
+}
+
+.progress-bar__step {
+  display: flex;
+  align-items: center;
+}
+
+.progress-bar__connector {
+  width: 40px;
+  height: 2px;
+  margin: 0 4px;
+}
+
+.progress-bar__connector--active {
+  background-color: var(--color-primary);
+}
+
+.progress-bar__connector--inactive {
+  background-color: var(--color-border);
+}
+
+.progress-bar__dot {
+  width: 32px;
+  height: 32px;
+  border-radius: 50%;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  font-weight: bold;
+  font-size: 0.85rem;
+  color: white;
+  margin: 0 auto 4px;
+}
+
+.progress-bar__dot--done,
+.progress-bar__dot--active {
+  background-color: var(--color-primary);
+}
+
+.progress-bar__dot--active {
+  border: 2px solid #4499ff;
+}
+
+.progress-bar__dot--pending {
+  background-color: var(--color-bg-card);
+  border: 2px solid transparent;
+}
+
+.progress-bar__label {
+  font-size: 0.7rem;
+  white-space: nowrap;
+}
+
+.progress-bar__label--active {
+  color: white;
+}
+
+.progress-bar__label--inactive {
+  color: #888;
+}
+
+/* Step 5 summary */
+.onboarding__summary {
+  background-color: #1e2e1e;
+  border: 1px solid #2d5a2d;
+  border-radius: var(--radius-lg);
+  padding: 1rem 1.25rem;
+  margin-bottom: 1.5rem;
+}
+
+.onboarding__summary-title {
+  margin: 0 0 0.5rem;
+  color: #90ee90;
+  font-weight: bold;
+}
+
+.onboarding__summary-list {
+  margin: 0;
+  padding-left: 1.25rem;
+  color: var(--color-text-label);
+  line-height: 1.8;
+}
+
+/* Checkbox rows */
+.checkbox-row {
+  margin-bottom: 1rem;
+}
+
+.checkbox-row__label {
+  display: flex;
+  align-items: center;
+  gap: 0.6rem;
+  cursor: pointer;
+  color: #ddd;
+}
+
+.checkbox-row__input {
+  width: 16px;
+  height: 16px;
+  accent-color: var(--color-primary);
+}
+
+.checkbox-row__nested {
+  margin-top: 0.5rem;
+  margin-left: 1.75rem;
+}
+
+/* Footer navigation */
+.onboarding__footer {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-top: 1.5rem;
+  padding-top: 1rem;
+  border-top: 1px solid var(--color-border-light);
+}
+
+/* Test results */
+.test-result {
+  font-size: 0.9rem;
+  margin-bottom: 0.25rem;
+}
+
+.test-result--success {
+  color: #90ee90;
+}
+
+.test-result--failure {
+  color: var(--color-error);
+}
+
+/* Step subtitle */
+.onboarding__subtitle {
+  color: #aaa;
+  margin-bottom: 1.5rem;
+  font-size: 0.9rem;
+}
+
+/* Subscribe card (Step 2) */
+.subscribe-card {
+  background-color: var(--color-bg-card, #1a1a2e);
+  border: 1px solid var(--color-border-light);
+  border-radius: var(--radius-lg);
+  padding: 1.5rem;
+  text-align: center;
+  margin-bottom: 1rem;
+}
+
+.subscribe-card__price {
+  margin-bottom: 1.25rem;
+}
+
+.subscribe-card__amount {
+  font-size: 2.5rem;
+  font-weight: 700;
+  color: white;
+}
+
+.subscribe-card__period {
+  font-size: 1rem;
+  color: #888;
+  margin-left: 2px;
+}
+
+.subscribe-card__features {
+  list-style: none;
+  padding: 0;
+  margin: 0 0 1.25rem;
+  text-align: left;
+}
+
+.subscribe-card__features li {
+  padding: 0.35rem 0;
+  color: #ccc;
+  font-size: 0.9rem;
+}
+
+.subscribe-card__features li::before {
+  content: "\2713";
+  color: var(--color-primary);
+  margin-right: 0.6rem;
+  font-weight: bold;
+}
+
+.subscribe-card__commitment {
+  color: #999;
+  font-size: 0.8rem;
+  margin: 0;
+  font-style: italic;
+}

frontend/src/pages/Onboarding.jsx

@@ -0,0 +1,671 @@
+/**
+ * Subscribe / Onboarding Wizard
+ *
+ * 5-step guided flow: Create Account -> Add Wallet -> Alert Rules -> Notifications -> Done
+ * After account creation, user is redirected to Stripe Checkout for payment.
+ * On successful payment, they return here at step 2 (Add Wallet).
+ */
+
+import { useState, useEffect } from "react";
+import { useNavigate, useSearchParams } from "react-router-dom";
+import { useAuth } from "../contexts/AuthContext";
+import { createAddress, getAddresses } from "../api/addresses";
+import { createAlert } from "../api/alerts";
+import {
+    updateNotificationConfig,
+    testNotificationChannels,
+} from "../api/notificationConfig";
+import { createCheckoutSession, getSubscriptionStatus } from "../api/stripe";
+import Input from "../components/Input";
+import Button from "../components/Button";
+import "./Onboarding.css";
+
+const STEPS = [
+    "Create Account",
+    "Add Wallet",
+    "Alert Rules",
+    "Notifications",
+    "Done",
+];
+
+export default function Onboarding() {
+    const { currentUser, signup } = useAuth();
+    const navigate = useNavigate();
+    const [searchParams, setSearchParams] = useSearchParams();
+
+    const [step, setStep] = useState(1);
+    const [loading, setLoading] = useState(false);
+    const [error, setError] = useState("");
+    const [skipWarning, setSkipWarning] = useState("");
+    const [testResults, setTestResults] = useState(null);
+    const [testLoading, setTestLoading] = useState(false);
+
+    const [data, setData] = useState({
+        email: "",
+        password: "",
+        confirmPassword: "",
+        walletAddress: "",
+        walletLabel: "",
+        createdAddressId: null,
+        alertIncomingTx: false,
+        alertOutgoingTx: false,
+        alertLargeTransfer: false,
+        largeTransferThreshold: "",
+        alertBalanceBelow: false,
+        balanceBelowThreshold: "",
+        discordWebhookUrl: "",
+        slackWebhookUrl: "",
+        notificationEmail: "",
+        alertsCreated: [],
+        notificationConfigured: false,
+    });
+
+    function set(field, value) {
+        setData((prev) => ({ ...prev, [field]: value }));
+    }
+
+    useEffect(() => {
+        if (!currentUser) return;
+        getAddresses()
+            .then((addresses) => {
+                if (addresses.length > 0) {
+                    navigate("/addresses", { replace: true });
+                }
+            })
+            .catch(() => {});
+    }, [currentUser, navigate]);
+
+    // Handle Stripe redirect back from checkout
+    useEffect(() => {
+        if (!currentUser) return;
+        const payment = searchParams.get("payment");
+        if (payment === "success") {
+            setSearchParams({}, { replace: true });
+            setStep(2);
+        } else if (payment === "cancelled") {
+            setSearchParams({}, { replace: true });
+            setStep(1);
+            setError("Payment was cancelled. Please try again.");
+        }
+    }, [currentUser, searchParams, setSearchParams]);
+
+    // ── Step handlers ─────────────────────────────────────────────────────────
+
+    async function handleStep1() {
+        setError("");
+        if (!data.email || !data.password || !data.confirmPassword) {
+            setError("Please fill in all fields");
+            return;
+        }
+        if (data.password !== data.confirmPassword) {
+            setError("Passwords do not match");
+            return;
+        }
+        if (data.password.length < 6) {
+            setError("Password must be at least 6 characters");
+            return;
+        }
+        try {
+            setLoading(true);
+            if (!currentUser) {
+                await signup(data.email, data.password);
+            }
+            const status = await getSubscriptionStatus();
+            if (status.subscription_status === "active" || status.subscription_status === "trialing") {
+                setStep(2);
+                return;
+            }
+            const { url } = await createCheckoutSession();
+            window.location.href = url;
+        } catch (err) {
+            if (err.code === "auth/email-already-in-use") {
+                setError("Email already in use. Try logging in instead.");
+            } else if (err.code === "auth/invalid-email") {
+                setError("Invalid email address");
+            } else if (err.code === "auth/weak-password") {
+                setError("Password is too weak");
+            } else {
+                setError("Failed to create account: " + err.message);
+            }
+            setLoading(false);
+        }
+    }
+
+    async function handleStep2() {
+        setError("");
+        if (!data.walletAddress) {
+            setError("Please enter a wallet address");
+            return;
+        }
+        if (!/^0x[0-9a-fA-F]{40}$/.test(data.walletAddress)) {
+            setError("Invalid ETH address (must be 0x followed by 40 hex characters)");
+            return;
+        }
+        try {
+            setLoading(true);
+            const created = await createAddress({
+                address: data.walletAddress,
+                label: data.walletLabel || undefined,
+            });
+            set("createdAddressId", created.id);
+            setStep(3);
+        } catch (err) {
+            setError(err.message);
+        } finally {
+            setLoading(false);
+        }
+    }
+
+    async function handleStep3() {
+        setError("");
+        const rules = [];
+        if (data.alertIncomingTx) rules.push({ type: "incoming_tx" });
+        if (data.alertOutgoingTx) rules.push({ type: "outgoing_tx" });
+        if (data.alertLargeTransfer) {
+            if (!data.largeTransferThreshold) {
+                setError("Please enter a threshold for large transfers");
+                return;
+            }
+            rules.push({ type: "large_transfer", threshold: data.largeTransferThreshold });
+        }
+        if (data.alertBalanceBelow) {
+            if (!data.balanceBelowThreshold) {
+                setError("Please enter a threshold for balance below");
+                return;
+            }
+            rules.push({ type: "balance_below", threshold: data.balanceBelowThreshold });
+        }
+
+        if (rules.length === 0) {
+            setStep(4);
+            return;
+        }
+
+        try {
+            setLoading(true);
+            const created = [];
+            for (const rule of rules) {
+                const result = await createAlert(data.createdAddressId, rule);
+                created.push(result);
+            }
+            set("alertsCreated", created);
+            setStep(4);
+        } catch (err) {
+            setError(err.message);
+        } finally {
+            setLoading(false);
+        }
+    }
+
+    async function handleStep4() {
+        setError("");
+        const hasAny =
+            data.discordWebhookUrl || data.slackWebhookUrl || data.notificationEmail;
+        if (!hasAny) {
+            setStep(5);
+            return;
+        }
+        try {
+            setLoading(true);
+            await updateNotificationConfig({
+                notification_enabled: true,
+                discord_webhook_url: data.discordWebhookUrl || undefined,
+                slack_webhook_url: data.slackWebhookUrl || undefined,
+                email: data.notificationEmail || undefined,
+            });
+            set("notificationConfigured", true);
+            setStep(5);
+        } catch (err) {
+            setError(err.message);
+        } finally {
+            setLoading(false);
+        }
+    }
+
+    async function handleTestChannels() {
+        setTestLoading(true);
+        setTestResults(null);
+        try {
+            const results = await testNotificationChannels();
+            setTestResults(results);
+        } catch (err) {
+            setTestResults({ error: err.message });
+        } finally {
+            setTestLoading(false);
+        }
+    }
+
+    // ── Progress bar ──────────────────────────────────────────────────────────
+
+    function ProgressBar() {
+        return (
+            <div className="progress-bar">
+                {STEPS.map((label, i) => {
+                    const stepNum = i + 1;
+                    const done = step > stepNum;
+                    const active = step === stepNum;
+                    const dotClass = done
+                        ? "progress-bar__dot--done"
+                        : active
+                          ? "progress-bar__dot--active"
+                          : "progress-bar__dot--pending";
+
+                    return (
+                        <div key={label} className="progress-bar__step">
+                            {i > 0 && (
+                                <div
+                                    className={`progress-bar__connector ${
+                                        done || active
+                                            ? "progress-bar__connector--active"
+                                            : "progress-bar__connector--inactive"
+                                    }`}
+                                />
+                            )}
+                            <div>
+                                <div className={`progress-bar__dot ${dotClass}`}>
+                                    {done ? "\u2713" : stepNum}
+                                </div>
+                                <div
+                                    className={`progress-bar__label ${
+                                        active
+                                            ? "progress-bar__label--active"
+                                            : "progress-bar__label--inactive"
+                                    }`}
+                                >
+                                    {label}
+                                </div>
+                            </div>
+                        </div>
+                    );
+                })}
+            </div>
+        );
+    }
+
+    // ── Step content ──────────────────────────────────────────────────────────
+
+    function Step1() {
+        return (
+            <>
+                <h2 className="mb-lg">Create your account</h2>
+                <Input
+                    label="Email"
+                    type="email"
+                    value={data.email}
+                    onChange={(v) => set("email", v)}
+                    disabled={loading}
+                    placeholder="you@example.com"
+                />
+                <Input
+                    label="Password"
+                    type="password"
+                    value={data.password}
+                    onChange={(v) => set("password", v)}
+                    disabled={loading}
+                    placeholder="At least 6 characters"
+                />
+                <Input
+                    label="Confirm Password"
+                    type="password"
+                    value={data.confirmPassword}
+                    onChange={(v) => set("confirmPassword", v)}
+                    disabled={loading}
+                    placeholder="Repeat your password"
+                    className="form-field--last"
+                />
+            </>
+        );
+    }
+
+    function Step2() {
+        return (
+            <>
+                <h2 className="mb-sm">Add a wallet address</h2>
+                <p className="onboarding__subtitle">
+                    Enter the Ethereum address you want to monitor.
+                </p>
+                <Input
+                    label="ETH Address"
+                    value={data.walletAddress}
+                    onChange={(v) => set("walletAddress", v)}
+                    disabled={loading}
+                    placeholder="0x..."
+                />
+                <Input
+                    label="Label (optional)"
+                    value={data.walletLabel}
+                    onChange={(v) => set("walletLabel", v)}
+                    disabled={loading}
+                    placeholder="e.g. My main wallet"
+                    className="form-field--last"
+                />
+            </>
+        );
+    }
+
+    function Step3() {
+        return (
+            <>
+                <h2 className="mb-sm">Configure alert rules</h2>
+                <p className="onboarding__subtitle">
+                    Choose which events trigger notifications. You can change these later.
+                </p>
+
+                <CheckboxRow
+                    checked={data.alertIncomingTx}
+                    onChange={(v) => set("alertIncomingTx", v)}
+                    label="Incoming transaction"
+                />
+                <CheckboxRow
+                    checked={data.alertOutgoingTx}
+                    onChange={(v) => set("alertOutgoingTx", v)}
+                    label="Outgoing transaction"
+                />
+                <CheckboxRow
+                    checked={data.alertLargeTransfer}
+                    onChange={(v) => set("alertLargeTransfer", v)}
+                    label="Large transfer"
+                >
+                    {data.alertLargeTransfer && (
+                        <div className="checkbox-row__nested">
+                            <Input
+                                type="number"
+                                label=""
+                                value={data.largeTransferThreshold}
+                                onChange={(v) => set("largeTransferThreshold", v)}
+                                placeholder="Threshold (ETH)"
+                                min="0"
+                                step="0.01"
+                            />
+                        </div>
+                    )}
+                </CheckboxRow>
+                <CheckboxRow
+                    checked={data.alertBalanceBelow}
+                    onChange={(v) => set("alertBalanceBelow", v)}
+                    label="Balance below"
+                >
+                    {data.alertBalanceBelow && (
+                        <div className="checkbox-row__nested">
+                            <Input
+                                type="number"
+                                label=""
+                                value={data.balanceBelowThreshold}
+                                onChange={(v) => set("balanceBelowThreshold", v)}
+                                placeholder="Threshold (ETH)"
+                                min="0"
+                                step="0.01"
+                            />
+                        </div>
+                    )}
+                </CheckboxRow>
+            </>
+        );
+    }
+
+    function Step4() {
+        return (
+            <>
+                <h2 className="mb-sm">Set up notifications</h2>
+                <p className="onboarding__subtitle">
+                    Add at least one channel so you receive alerts. All fields are optional.
+                </p>
+
+                <div className="mb-md">
+                    <label className="form-label">
+                        Discord Webhook URL{" "}
+                        <a
+                            href="https://support.discord.com/hc/en-us/articles/228383668"
+                            target="_blank"
+                            rel="noreferrer"
+                            className="help-link"
+                        >
+                            (how to get one)
+                        </a>
+                    </label>
+                    <Input
+                        label=""
+                        type="url"
+                        value={data.discordWebhookUrl}
+                        onChange={(v) => set("discordWebhookUrl", v)}
+                        disabled={loading}
+                        placeholder="https://discord.com/api/webhooks/..."
+                    />
+                </div>
+
+                <div className="mb-md">
+                    <label className="form-label">
+                        Slack Webhook URL{" "}
+                        <a
+                            href="https://api.slack.com/messaging/webhooks"
+                            target="_blank"
+                            rel="noreferrer"
+                            className="help-link"
+                        >
+                            (how to get one)
+                        </a>
+                    </label>
+                    <Input
+                        label=""
+                        type="url"
+                        value={data.slackWebhookUrl}
+                        onChange={(v) => set("slackWebhookUrl", v)}
+                        disabled={loading}
+                        placeholder="https://hooks.slack.com/services/..."
+                    />
+                </div>
+
+                <Input
+                    label="Email address for alerts"
+                    type="email"
+                    value={data.notificationEmail}
+                    onChange={(v) => set("notificationEmail", v)}
+                    disabled={loading}
+                    placeholder="you@example.com"
+                    className="form-field--last"
+                />
+            </>
+        );
+    }
+
+    function Step5() {
+        const alertCount = data.alertsCreated.length;
+        const hasNotif = data.notificationConfigured;
+
+        return (
+            <>
+                <h2 className="mb-md">You're all set!</h2>
+
+                <div className="onboarding__summary">
+                    <p className="onboarding__summary-title">Summary</p>
+                    <ul className="onboarding__summary-list">
+                        <li>
+                            Wallet address added:{" "}
+                            <span className="text-mono text-white-sm">
+                                {data.walletAddress}
+                            </span>
+                            {data.walletLabel && ` (${data.walletLabel})`}
+                        </li>
+                        <li>
+                            Alert rules configured:{" "}
+                            <span className="text-white">
+                                {alertCount > 0 ? `${alertCount} rule${alertCount !== 1 ? "s" : ""}` : "None (skipped)"}
+                            </span>
+                        </li>
+                        <li>
+                            Notification channels:{" "}
+                            <span className="text-white">
+                                {hasNotif ? "Configured" : "Not set up (skipped)"}
+                            </span>
+                        </li>
+                    </ul>
+                </div>
+
+                {hasNotif && (
+                    <div className="mb-lg">
+                        <Button
+                            onClick={handleTestChannels}
+                            disabled={testLoading}
+                            variant="ghost"
+                        >
+                            {testLoading ? "Testing..." : "Test All Channels"}
+                        </Button>
+
+                        {testResults && (
+                            <div className="mt-md">
+                                {testResults.error ? (
+                                    <p className="text-error">{testResults.error}</p>
+                                ) : (
+                                    <ul className="list-unstyled">
+                                        {Object.entries(testResults).map(([channel, result]) => (
+                                            <li
+                                                key={channel}
+                                                className={`test-result ${result.success ? "test-result--success" : "test-result--failure"}`}
+                                            >
+                                                {result.success ? "\u2713" : "\u2717"} {channel}:{" "}
+                                                {result.message || (result.success ? "OK" : "Failed")}
+                                            </li>
+                                        ))}
+                                    </ul>
+                                )}
+                            </div>
+                        )}
+                    </div>
+                )}
+
+                <Button onClick={() => navigate("/addresses")} className="btn--lg text-bold">
+                    Go to Dashboard →
+                </Button>
+            </>
+        );
+    }
+
+    // ── Shared helpers ────────────────────────────────────────────────────────
+
+    function CheckboxRow({ checked, onChange, label, children }) {
+        return (
+            <div className="checkbox-row">
+                <label className="checkbox-row__label">
+                    <input
+                        type="checkbox"
+                        checked={checked}
+                        onChange={(e) => onChange(e.target.checked)}
+                        className="checkbox-row__input"
+                    />
+                    {label}
+                </label>
+                {children}
+            </div>
+        );
+    }
+
+    // ── Footer navigation ─────────────────────────────────────────────────────
+
+    function Footer() {
+        if (step === 5) return null;
+
+        const canSkip = step === 3 || step === 4;
+        const canBack = step > 2;
+
+        async function handleNext() {
+            setSkipWarning("");
+            if (step === 1) await handleStep1();
+            else if (step === 2) await handleStep2();
+            else if (step === 3) await handleStep3();
+            else if (step === 4) await handleStep4();
+        }
+
+        function handleSkip() {
+            setError("");
+            setSkipWarning("");
+            setStep((s) => s + 1);
+        }
+
+        function handleBack() {
+            setError("");
+            setSkipWarning("");
+            setStep((s) => s - 1);
+        }
+
+        const nextLabel = step === 1
+            ? "Create Account & Subscribe"
+            : step === 4
+              ? "Finish"
+              : "Next →";
+
+        return (
+            <div className="onboarding__footer">
+                <div>
+                    {canBack && (
+                        <Button
+                            onClick={handleBack}
+                            disabled={loading}
+                            variant="ghost"
+                        >
+                            ← Back
+                        </Button>
+                    )}
+                </div>
+
+                <div className="flex gap-md">
+                    {canSkip && (
+                        <Button
+                            onClick={handleSkip}
+                            disabled={loading}
+                            variant="ghost"
+                        >
+                            Skip for now
+                        </Button>
+                    )}
+                    <Button
+                        onClick={handleNext}
+                        disabled={loading}
+                        className="text-bold"
+                    >
+                        {loading ? "Please wait..." : nextLabel}
+                    </Button>
+                </div>
+            </div>
+        );
+    }
+
+    // ── Render ────────────────────────────────────────────────────────────────
+
+    const stepContent = {
+        1: Step1(),
+        2: Step2(),
+        3: Step3(),
+        4: Step4(),
+        5: Step5(),
+    };
+
+    return (
+        <div className="onboarding">
+            <div className="onboarding__container">
+                <h1 className="onboarding__title">Koin Ping</h1>
+
+                {ProgressBar()}
+
+                {error && (
+                    <div className="alert alert--error">{error}</div>
+                )}
+
+                {skipWarning && (
+                    <div className="alert alert--warning">{skipWarning}</div>
+                )}
+
+                <div className="onboarding__card">
+                    {stepContent[step]}
+                    {Footer()}
+                </div>
+
+                {step === 1 && (
+                    <p className="onboarding__login-link">
+                        Already have an account?{" "}
+                        <a href="/login">Log in here</a>
+                    </p>
+                )}
+            </div>
+        </div>
+    );
+}

frontend/src/pages/Signup.jsx

@@ -1,188 +1,5 @@
-/**
- * Signup Page
- *
- * Allows new users to create an account with email and password
- */
-
-import { useState } from "react";
-import { Link, useNavigate } from "react-router-dom";
-import { useAuth } from "../contexts/AuthContext";
+import { Navigate } from "react-router-dom";
 
 export default function Signup() {
-    const [email, setEmail] = useState("");
-    const [password, setPassword] = useState("");
-    const [confirmPassword, setConfirmPassword] = useState("");
-    const [error, setError] = useState("");
-    const [loading, setLoading] = useState(false);
-
-    const { signup } = useAuth();
-    const navigate = useNavigate();
-
-    async function handleSubmit(e) {
-        e.preventDefault();
-
-        // Validation
-        if (!email || !password || !confirmPassword) {
-            setError("Please fill in all fields");
-            return;
-        }
-
-        if (password !== confirmPassword) {
-            setError("Passwords do not match");
-            return;
-        }
-
-        if (password.length < 6) {
-            setError("Password must be at least 6 characters");
-            return;
-        }
-
-        try {
-            setError("");
-            setLoading(true);
-            await signup(email, password);
-            navigate("/addresses"); // Auto-login and redirect
-        } catch (err) {
-            // Firebase-specific error messages
-            if (err.code === "auth/email-already-in-use") {
-                setError("Email already in use. Try logging in instead.");
-            } else if (err.code === "auth/invalid-email") {
-                setError("Invalid email address");
-            } else if (err.code === "auth/weak-password") {
-                setError("Password is too weak");
-            } else {
-                setError("Failed to create account: " + err.message);
-            }
-        } finally {
-            setLoading(false);
-        }
-    }
-
-    return (
-        <div
-            style={{
-                maxWidth: "400px",
-                margin: "4rem auto",
-                padding: "2rem",
-                border: "1px solid #333",
-                borderRadius: "8px",
-            }}
-        >
-            <h1 style={{ marginBottom: "2rem", textAlign: "center" }}>
-                Koin Ping - Sign Up
-            </h1>
-
-            {error && (
-                <div
-                    style={{
-                        padding: "0.75rem",
-                        marginBottom: "1rem",
-                        backgroundColor: "#ff000020",
-                        border: "1px solid #ff0000",
-                        borderRadius: "4px",
-                        color: "#ff6666",
-                    }}
-                >
-                    {error}
-                </div>
-            )}
-
-            <form onSubmit={handleSubmit}>
-                <div style={{ marginBottom: "1rem" }}>
-                    <label style={{ display: "block", marginBottom: "0.5rem" }}>
-                        Email
-                    </label>
-                    <input
-                        type="email"
-                        value={email}
-                        onChange={(e) => setEmail(e.target.value)}
-                        disabled={loading}
-                        style={{
-                            width: "100%",
-                            padding: "0.5rem",
-                            fontSize: "1rem",
-                            backgroundColor: "#242424",
-                            border: "1px solid #444",
-                            borderRadius: "4px",
-                            color: "white",
-                        }}
-                        required
-                    />
-                </div>
-
-                <div style={{ marginBottom: "1rem" }}>
-                    <label style={{ display: "block", marginBottom: "0.5rem" }}>
-                        Password
-                    </label>
-                    <input
-                        type="password"
-                        value={password}
-                        onChange={(e) => setPassword(e.target.value)}
-                        disabled={loading}
-                        style={{
-                            width: "100%",
-                            padding: "0.5rem",
-                            fontSize: "1rem",
-                            backgroundColor: "#242424",
-                            border: "1px solid #444",
-                            borderRadius: "4px",
-                            color: "white",
-                        }}
-                        required
-                    />
-                </div>
-
-                <div style={{ marginBottom: "1.5rem" }}>
-                    <label style={{ display: "block", marginBottom: "0.5rem" }}>
-                        Confirm Password
-                    </label>
-                    <input
-                        type="password"
-                        value={confirmPassword}
-                        onChange={(e) => setConfirmPassword(e.target.value)}
-                        disabled={loading}
-                        style={{
-                            width: "100%",
-                            padding: "0.5rem",
-                            fontSize: "1rem",
-                            backgroundColor: "#242424",
-                            border: "1px solid #444",
-                            borderRadius: "4px",
-                            color: "white",
-                        }}
-                        required
-                    />
-                </div>
-
-                <button
-                    type="submit"
-                    disabled={loading}
-                    style={{
-                        width: "100%",
-                        padding: "0.75rem",
-                        fontSize: "1rem",
-                        backgroundColor: loading ? "#333" : "#0066cc",
-                        color: "white",
-                        border: "none",
-                        borderRadius: "4px",
-                        cursor: loading ? "not-allowed" : "pointer",
-                    }}
-                >
-                    {loading ? "Creating account..." : "Sign Up"}
-                </button>
-            </form>
-
-            <div style={{ marginTop: "1.5rem", textAlign: "center" }}>
-                <p style={{ color: "#b3b3b3" }}>
-                    Already have an account?{" "}
-                    <Link
-                        to="/login"
-                        style={{ color: "#0066cc", textDecoration: "none" }}
-                    >
-                        Log in here
-                    </Link>
-                </p>
-            </div>
-        </div>
-    );
+    return <Navigate to="/subscribe" replace />;
 }