general cleanup - removed old comments, enforced naming conventions etc

backend/infra/migrations/002_add_notification_config.sql

@@ -0,0 +1,13 @@
+
+CREATE TABLE user_notification_configs (
+  user_id VARCHAR(128) PRIMARY KEY,
+  discord_webhook_url TEXT,
+  telegram_chat_id VARCHAR(128),
+  telegram_bot_token VARCHAR(255),
+  email VARCHAR(255),
+  notification_enabled BOOLEAN DEFAULT TRUE,
+  created_at TIMESTAMP DEFAULT NOW(),
+  updated_at TIMESTAMP DEFAULT NOW()
+);
+
+CREATE INDEX idx_notification_configs_enabled ON user_notification_configs(notification_enabled);