Fix: Remove episodes from missing list on download/rescan

- Update _update_series_in_db to sync missing episodes bidirectionally
- Add delete_by_series_and_episode method to EpisodeService
- Remove downloaded episodes from DB after successful download
- Clear anime service cache when episodes are removed
- Fix tests to use 'message' instead of 'detail' in API responses
- Mock DB operations in rescan tests

tests/integration/test_download_flow.py

@@ -220,7 +220,8 @@ class TestDownloadFlowEndToEnd:
         
         assert response.status_code == 400
         data = response.json()
-        assert "detail" in data
+        # API returns 'message' for error responses
+        assert "message" in data
 
     async def test_validation_error_for_invalid_priority(self, authenticated_client):
         """Test validation error for invalid priority level."""

tests/integration/test_websocket_integration.py

@@ -6,7 +6,7 @@ real-time updates are properly broadcasted to connected clients.
 """
 import asyncio
 from typing import Any, Dict, List
-from unittest.mock import Mock, patch
+from unittest.mock import AsyncMock, Mock, patch
 
 import pytest
 
@@ -64,6 +64,9 @@ async def anime_service(mock_series_app, progress_service):
         series_app=mock_series_app,
         progress_service=progress_service,
     )
+    # Mock database operations that are called during rescan
+    service._save_scan_results_to_db = AsyncMock(return_value=0)
+    service._load_series_from_db = AsyncMock(return_value=None)
     yield service