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/database/database.go

@@ -133,7 +133,9 @@ func Migrate() error {
 		&models.Contractor{},  // Contractor before Task (Task references Contractor)
 		&models.Task{},
 		&models.TaskCompletion{},
+		&models.TaskCompletionImage{}, // Multiple images per completion
 		&models.Document{},
+		&models.DocumentImage{}, // Multiple images per document
 
 		// Notification tables
 		&models.Notification{},