refactoring backup

src/server/services/download_service.py

@@ -71,7 +71,7 @@ class DownloadService:
         self._max_retries = max_retries
         self._persistence_path = Path(persistence_path)
         self._progress_service = progress_service or get_progress_service()
-        
+      
         # Queue storage by status
         self._pending_queue: deque[DownloadItem] = deque()
         # Helper dict for O(1) lookup of pending items by ID
@@ -92,7 +92,7 @@ class DownloadService:
         # Statistics tracking
         self._total_downloaded_mb: float = 0.0
         self._download_speeds: deque[float] = deque(maxlen=10)
-        
+     
         # Load persisted queue
         self._load_queue()