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>

internal/worker/jobs/handler.go

@@ -18,29 +18,38 @@ import (
 
 // Task types
 const (
-	TypeTaskReminder    = "notification:task_reminder"
-	TypeOverdueReminder = "notification:overdue_reminder"
-	TypeDailyDigest     = "notification:daily_digest"
-	TypeSendEmail       = "email:send"
-	TypeSendPush        = "push:send"
+	TypeTaskReminder     = "notification:task_reminder"
+	TypeOverdueReminder  = "notification:overdue_reminder"
+	TypeDailyDigest      = "notification:daily_digest"
+	TypeSendEmail        = "email:send"
+	TypeSendPush         = "push:send"
+	TypeOnboardingEmails = "email:onboarding"
 )
 
 // Handler handles background job processing
 type Handler struct {
-	db                  *gorm.DB
-	pushClient          *push.Client
-	emailService        *services.EmailService
-	notificationService *services.NotificationService
-	config              *config.Config
+	db                   *gorm.DB
+	pushClient           *push.Client
+	emailService         *services.EmailService
+	notificationService  *services.NotificationService
+	onboardingService    *services.OnboardingEmailService
+	config               *config.Config
 }
 
 // NewHandler creates a new job handler
 func NewHandler(db *gorm.DB, pushClient *push.Client, emailService *services.EmailService, notificationService *services.NotificationService, cfg *config.Config) *Handler {
+	// Create onboarding email service
+	var onboardingService *services.OnboardingEmailService
+	if emailService != nil {
+		onboardingService = services.NewOnboardingEmailService(db, emailService, cfg.Server.BaseURL)
+	}
+
 	return &Handler{
 		db:                  db,
 		pushClient:          pushClient,
 		emailService:        emailService,
 		notificationService: notificationService,
+		onboardingService:   onboardingService,
 		config:              cfg,
 	}
 }
@@ -514,3 +523,41 @@ func NewSendPushTask(userID uint, title, message string, data map[string]string)
 	}
 	return asynq.NewTask(TypeSendPush, payload), nil
 }
+
+// HandleOnboardingEmails processes onboarding email campaigns
+// Sends emails to:
+// 1. Users who registered 2+ days ago but haven't created a residence
+// 2. Users who created a residence 5+ days ago but haven't created any tasks
+// Each email type is only sent once per user, ever.
+func (h *Handler) HandleOnboardingEmails(ctx context.Context, task *asynq.Task) error {
+	log.Info().Msg("Processing onboarding emails...")
+
+	if h.onboardingService == nil {
+		log.Warn().Msg("Onboarding email service not configured, skipping")
+		return nil
+	}
+
+	// Send no-residence emails (users without any residences after 2 days)
+	noResCount, err := h.onboardingService.CheckAndSendNoResidenceEmails()
+	if err != nil {
+		log.Error().Err(err).Msg("Failed to process no-residence onboarding emails")
+		// Continue to next type, don't return error
+	} else {
+		log.Info().Int("count", noResCount).Msg("Sent no-residence onboarding emails")
+	}
+
+	// Send no-tasks emails (users with residence but no tasks after 5 days)
+	noTasksCount, err := h.onboardingService.CheckAndSendNoTasksEmails()
+	if err != nil {
+		log.Error().Err(err).Msg("Failed to process no-tasks onboarding emails")
+	} else {
+		log.Info().Int("count", noTasksCount).Msg("Sent no-tasks onboarding emails")
+	}
+
+	log.Info().
+		Int("no_residence_sent", noResCount).
+		Int("no_tasks_sent", noTasksCount).
+		Msg("Onboarding email processing completed")
+
+	return nil
+}