Add onboarding email campaign system with post-verification welcome email

Implements automated onboarding emails to encourage user engagement:
- Post-verification welcome email with 5 tips (sent after email verification)
- "No Residence" email (2+ days after registration with no property)
- "No Tasks" email (5+ days after first residence with no tasks)

Key features:
- Each onboarding email type sent only once per user (enforced by unique constraint)
- Email open tracking via tracking pixel endpoint
- Daily scheduled job at 10:00 AM UTC to process eligible users
- Admin panel UI for viewing sent emails, stats, and manual sending
- Admin can send any email type to users from the user detail Testing section

New files:
- internal/models/onboarding_email.go - Database model with tracking
- internal/services/onboarding_email_service.go - Business logic and eligibility queries
- internal/handlers/tracking_handler.go - Email open tracking endpoint
- internal/admin/handlers/onboarding_handler.go - Admin API endpoints
- admin/src/app/(dashboard)/onboarding-emails/ - Admin UI pages

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

cmd/worker/main.go

@@ -100,6 +100,7 @@ func main() {
 	mux.HandleFunc(jobs.TypeDailyDigest, jobHandler.HandleDailyDigest)
 	mux.HandleFunc(jobs.TypeSendEmail, jobHandler.HandleSendEmail)
 	mux.HandleFunc(jobs.TypeSendPush, jobHandler.HandleSendPush)
+	mux.HandleFunc(jobs.TypeOnboardingEmails, jobHandler.HandleOnboardingEmails)
 
 	// Start scheduler for periodic tasks
 	scheduler := asynq.NewScheduler(redisOpt, nil)
@@ -124,6 +125,13 @@ func main() {
 	}
 	log.Info().Str("cron", "0 * * * *").Int("default_hour", cfg.Worker.DailyNotifHour).Msg("Registered daily digest job (runs hourly for per-user times)")
 
+	// Schedule onboarding emails (runs daily at 10:00 AM UTC)
+	// Sends emails to users who haven't created residences or tasks after registration
+	if _, err := scheduler.Register("0 10 * * *", asynq.NewTask(jobs.TypeOnboardingEmails, nil)); err != nil {
+		log.Fatal().Err(err).Msg("Failed to register onboarding emails job")
+	}
+	log.Info().Str("cron", "0 10 * * *").Msg("Registered onboarding emails job (runs daily at 10:00 AM UTC)")
+
 	// Handle graceful shutdown
 	quit := make(chan os.Signal, 1)
 	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)