feat: Implement download queue API endpoints

- Add comprehensive REST API for download queue management
- Implement GET /api/queue/status endpoint with queue status and statistics
- Implement POST /api/queue/add for adding episodes to queue with priority support
- Implement DELETE /api/queue/{id} and DELETE /api/queue/ for removing items
- Implement POST /api/queue/start and /api/queue/stop for queue control
- Implement POST /api/queue/pause and /api/queue/resume for pause/resume
- Implement POST /api/queue/reorder for queue item reordering
- Implement DELETE /api/queue/completed for clearing completed items
- Implement POST /api/queue/retry for retrying failed downloads
- Add get_download_service and get_anime_service dependencies
- Register download router in FastAPI application
- Add comprehensive test suite for all endpoints
- All endpoints require JWT authentication
- Update infrastructure documentation
- Remove completed task from instructions.md

Follows REST conventions with proper error handling and status codes.
Tests cover success cases, error conditions, and authentication requirements.

src/server/utils/dependencies.py

@@ -2,8 +2,8 @@
 Dependency injection utilities for FastAPI.
 
 This module provides dependency injection functions for the FastAPI
-application, including SeriesApp instances, database sessions, and
-authentication dependencies.
+application, including SeriesApp instances, AnimeService, DownloadService,
+database sessions, and authentication dependencies.
 """
 from typing import AsyncGenerator, Optional
 
@@ -26,6 +26,10 @@ security = HTTPBearer()
 # Global SeriesApp instance
 _series_app: Optional[SeriesApp] = None
 
+# Global service instances
+_anime_service: Optional[object] = None
+_download_service: Optional[object] = None
+
 
 def get_series_app() -> SeriesApp:
     """
@@ -193,3 +197,79 @@ async def log_request_dependency():
     TODO: Implement request logging logic
     """
     pass
+
+
+def get_anime_service() -> object:
+    """
+    Dependency to get AnimeService instance.
+    
+    Returns:
+        AnimeService: The anime service for async operations
+        
+    Raises:
+        HTTPException: If anime directory is not configured or
+                      AnimeService initialization fails
+    """
+    global _anime_service
+    
+    if not settings.anime_directory:
+        raise HTTPException(
+            status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
+            detail="Anime directory not configured. Please complete setup.",
+        )
+    
+    if _anime_service is None:
+        try:
+            from src.server.services.anime_service import AnimeService
+            _anime_service = AnimeService(settings.anime_directory)
+        except Exception as e:
+            raise HTTPException(
+                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+                detail=f"Failed to initialize AnimeService: {str(e)}",
+            ) from e
+    
+    return _anime_service
+
+
+def get_download_service() -> object:
+    """
+    Dependency to get DownloadService instance.
+    
+    Returns:
+        DownloadService: The download queue service
+        
+    Raises:
+        HTTPException: If DownloadService initialization fails
+    """
+    global _download_service
+    
+    if _download_service is None:
+        try:
+            from src.server.services.download_service import DownloadService
+
+            # Get anime service first (required dependency)
+            anime_service = get_anime_service()
+            
+            # Initialize download service with anime service
+            _download_service = DownloadService(anime_service)
+        except HTTPException:
+            raise
+        except Exception as e:
+            raise HTTPException(
+                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+                detail=f"Failed to initialize DownloadService: {str(e)}",
+            ) from e
+    
+    return _download_service
+
+
+def reset_anime_service() -> None:
+    """Reset global AnimeService instance (for testing/config changes)."""
+    global _anime_service
+    _anime_service = None
+
+
+def reset_download_service() -> None:
+    """Reset global DownloadService instance (for testing/config changes)."""
+    global _download_service
+    _download_service = None