first commit of refactor

backend/infra/add_notification_config.sql

@@ -0,0 +1,21 @@
+
+-- Run: psql -d koin_ping_dev -f add_notification_config.sql
+
+-- Create user notification configuration tableStores notification preferences and webhook URLs for each user
+CREATE TABLE user_notification_configs (
+  user_id VARCHAR(128) PRIMARY KEY,
+  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, future use)
+  email VARCHAR(255),                  -- Email for notifications (nullable)
+  notification_enabled BOOLEAN DEFAULT TRUE,  -- Master on/off switch
+  created_at TIMESTAMP DEFAULT NOW(),
+  updated_at TIMESTAMP DEFAULT NOW()
+);
+
+-- Create index for active notifications lookup
+CREATE INDEX idx_notification_configs_enabled ON user_notification_configs(notification_enabled);
+
+-- Note: No foreign key to a users table (doesn't exist yet)
+-- user_id is the Firebase UID, validated by backend middleware
+