Fix: Add graceful download cancellation on Ctrl+C

- Add cancellation flag to AniworldLoader with request_cancel/reset_cancel/is_cancelled methods
- Update base_provider.Loader interface with cancellation abstract methods
- Integrate cancellation check in YT-DLP progress hooks
- Add request_download_cancel method to SeriesApp and AnimeService
- Update DownloadService.stop() to request cancellation before shutdown
- Clean up temp files on cancellation

src/core/providers/base_provider.py

@@ -5,6 +5,30 @@ from typing import Any, Callable, Dict, List, Optional
 class Loader(ABC):
     """Abstract base class for anime data loaders/providers."""
 
+    @abstractmethod
+    def request_cancel(self) -> None:
+        """Request cancellation of any ongoing download.
+        
+        Sets an internal flag that downloads should check periodically
+        and abort if set. This enables graceful shutdown.
+        """
+
+    @abstractmethod
+    def reset_cancel(self) -> None:
+        """Reset the cancellation flag.
+        
+        Should be called before starting a new download to ensure
+        it's not immediately cancelled.
+        """
+
+    @abstractmethod
+    def is_cancelled(self) -> bool:
+        """Check if cancellation has been requested.
+        
+        Returns:
+            bool: True if cancellation was requested
+        """
+
     @abstractmethod
     def search(self, word: str) -> List[Dict[str, Any]]:
         """Search for anime series by name.