Add webhook logging, pagination, middleware, migrations, and prod hardening

- Webhook event logging repo and subscription webhook idempotency
- Pagination helper (echohelpers) with cursor/offset support
- Request ID and structured logging middleware
- Push client improvements (FCM HTTP v1, better error handling)
- Task model version column, business constraint migrations, targeted indexes
- Expanded categorization chain tests
- Email service and config hardening
- CI workflow updates, .gitignore additions, .env.example updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/integration/subscription_is_free_test.go

@@ -63,7 +63,7 @@ func setupSubscriptionTest(t *testing.T) *SubscriptionTestApp {
 
 	// Create handlers
 	authHandler := handlers.NewAuthHandler(authService, nil, nil)
-	residenceHandler := handlers.NewResidenceHandler(residenceService, nil, nil)
+	residenceHandler := handlers.NewResidenceHandler(residenceService, nil, nil, true)
 	subscriptionHandler := handlers.NewSubscriptionHandler(subscriptionService)
 
 	// Create router