refactor: remove database access from core layer

- Remove db_session parameter from SeriesApp, SerieList, SerieScanner
- Move all database operations to AnimeService (service layer)
- Add add_series_to_db, contains_in_db methods to AnimeService
- Update sync_series_from_data_files to use inline DB operations
- Remove obsolete test classes for removed DB methods
- Fix pylint issues: add broad-except comments, fix line lengths
- Core layer (src/core/) now has zero database imports

722 unit tests pass

tests/unit/test_anime_service.py

@@ -6,7 +6,7 @@ error handling, and progress reporting integration.
 from __future__ import annotations
 
 import asyncio
-from unittest.mock import AsyncMock, MagicMock
+from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
 
@@ -183,7 +183,17 @@ class TestRescan:
         self, anime_service, mock_series_app, mock_progress_service
     ):
         """Test successful rescan operation."""
-        await anime_service.rescan()
+        # Mock rescan to return empty list (no DB save needed)
+        mock_series_app.rescan.return_value = []
+        
+        # Mock the database operations
+        with patch.object(
+            anime_service, '_save_scan_results_to_db', new_callable=AsyncMock
+        ):
+            with patch.object(
+                anime_service, '_load_series_from_db', new_callable=AsyncMock
+            ):
+                await anime_service.rescan()
         
         # Verify SeriesApp.rescan was called (lowercase, not ReScan)
         mock_series_app.rescan.assert_called_once()
@@ -193,7 +203,15 @@ class TestRescan:
         """Test rescan operation (callback parameter removed)."""
         # Rescan no longer accepts callback parameter
         # Progress is tracked via event handlers automatically
-        await anime_service.rescan()
+        mock_series_app.rescan.return_value = []
+        
+        with patch.object(
+            anime_service, '_save_scan_results_to_db', new_callable=AsyncMock
+        ):
+            with patch.object(
+                anime_service, '_load_series_from_db', new_callable=AsyncMock
+            ):
+                await anime_service.rescan()
         
         # Verify rescan was called
         mock_series_app.rescan.assert_called_once()
@@ -207,9 +225,17 @@ class TestRescan:
         
         # Update series list
         mock_series_app.series_list = [{"name": "Test"}, {"name": "New"}]
+        mock_series_app.rescan.return_value = []
         
-        # Rescan should clear cache
-        await anime_service.rescan()
+        # Mock the database operations
+        with patch.object(
+            anime_service, '_save_scan_results_to_db', new_callable=AsyncMock
+        ):
+            with patch.object(
+                anime_service, '_load_series_from_db', new_callable=AsyncMock
+            ):
+                # Rescan should clear cache
+                await anime_service.rescan()
         
         # Next list_missing should return updated data
         result = await anime_service.list_missing()