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/worker/main.go

@@ -31,6 +31,12 @@ func main() {
 		log.Fatal().Err(err).Msg("Failed to load configuration")
 	}
 
+	// Check worker kill switch
+	if !cfg.Features.WorkerEnabled {
+		log.Warn().Msg("Worker disabled by FEATURE_WORKER_ENABLED=false — exiting")
+		os.Exit(0)
+	}
+
 	// Initialize database
 	db, err := database.Connect(&cfg.Database, cfg.Server.Debug)
 	if err != nil {
@@ -44,7 +50,7 @@ func main() {
 
 	// Initialize push 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 {
@@ -57,7 +63,7 @@ func main() {
 	// Initialize email service (optional)
 	var emailService *services.EmailService
 	if cfg.Email.Host != "" {
-		emailService = services.NewEmailService(&cfg.Email)
+		emailService = services.NewEmailService(&cfg.Email, cfg.Features.EmailEnabled)
 		log.Info().Str("host", cfg.Email.Host).Msg("Email service initialized")
 	}
 
@@ -109,6 +115,12 @@ func main() {
 		}
 	}
 
+	// Check worker kill switch
+	if !cfg.Features.WorkerEnabled {
+		log.Warn().Msg("Worker disabled by FEATURE_WORKER_ENABLED=false, exiting")
+		return
+	}
+
 	// Create Asynq server
 	srv := asynq.NewServer(
 		redisOpt,