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/unit/test_serie_list.py

@@ -1,9 +1,9 @@
 """Tests for SerieList class - identifier standardization."""
+# pylint: disable=redefined-outer-name
 
 import os
 import tempfile
 import warnings
-from unittest.mock import MagicMock, patch
 
 import pytest