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>

cmd/api/main.go

@@ -111,7 +111,7 @@ func main() {
 		Int("email_port", cfg.Email.Port).
 		Msg("Email config loaded")
 	if cfg.Email.Host != "" && cfg.Email.User != "" {
-		emailService = services.NewEmailService(&cfg.Email)
+		emailService = services.NewEmailService(&cfg.Email, cfg.Features.EmailEnabled)
 		log.Info().
 			Str("host", cfg.Email.Host).
 			Msg("Email service initialized")
@@ -143,7 +143,7 @@ func main() {
 
 	// Initialize push notification client (APNs + FCM)
 	var pushClient *push.Client
-	pushClient, err = push.NewClient(&cfg.Push)
+	pushClient, err = push.NewClient(&cfg.Push, cfg.Features.PushEnabled)
 	if err != nil {
 		log.Warn().Err(err).Msg("Failed to initialize push client - push notifications disabled")
 	} else {