Add multi-image support for task completions and documents

- Add TaskCompletionImage and DocumentImage models with one-to-many relationships
- Update admin panel to display images for completions and documents
- Add image arrays to API request/response DTOs
- Update repositories with Preload("Images") for eager loading
- Fix seed SQL execution to use raw SQL instead of prepared statements
- Fix table names in seed file (admin_users, push_notifications_*)
- Add comprehensive seed test data with 34 completion images and 24 document images
- Add subscription limitations admin feature with toggle
- Update admin sidebar with limitations link

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

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

internal/router/router.go

@@ -325,6 +325,7 @@ func setupSubscriptionRoutes(api *gin.RouterGroup, subscriptionHandler *handlers
 	{
 		subscription.GET("/", subscriptionHandler.GetSubscription)
 		subscription.GET("/status/", subscriptionHandler.GetSubscriptionStatus)
+		subscription.GET("/upgrade-triggers/", subscriptionHandler.GetAllUpgradeTriggers)
 		subscription.GET("/upgrade-trigger/:key/", subscriptionHandler.GetUpgradeTrigger)
 		subscription.GET("/features/", subscriptionHandler.GetFeatureBenefits)
 		subscription.GET("/promotions/", subscriptionHandler.GetPromotions)