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/dto/requests/document.go

@@ -25,6 +25,7 @@ type CreateDocumentRequest struct {
 	SerialNumber  string               `json:"serial_number" binding:"max=100"`
 	ModelNumber   string               `json:"model_number" binding:"max=100"`
 	TaskID        *uint                `json:"task_id"`
+	ImageURLs     []string             `json:"image_urls"` // Multiple image URLs
 }
 
 // UpdateDocumentRequest represents the request to update a document