refactor: move sync_series_from_data_files to anime_service

- Moved _sync_series_to_database from fastapi_app.py to anime_service.py
- Renamed to sync_series_from_data_files for better clarity
- Updated all imports and test references
- Removed completed TODO tasks from instructions.md

tests/integration/test_data_file_db_sync.py

@@ -187,19 +187,19 @@ class TestSerieListAddToDb:
 
 
 class TestSyncSeriesToDatabase:
-    """Test _sync_series_to_database function from fastapi_app."""
+    """Test sync_series_from_data_files function from anime_service."""
 
     @pytest.mark.asyncio
     async def test_sync_with_empty_directory(self):
         """Test sync with empty anime directory."""
-        from src.server.fastapi_app import _sync_series_to_database
+        from src.server.services.anime_service import sync_series_from_data_files
 
         with tempfile.TemporaryDirectory() as tmp_dir:
             mock_logger = Mock()
 
             with patch('src.core.SeriesApp.Loaders'), \
                  patch('src.core.SeriesApp.SerieScanner'):
-                count = await _sync_series_to_database(tmp_dir, mock_logger)
+                count = await sync_series_from_data_files(tmp_dir, mock_logger)
 
                 assert count == 0
                 # Should log that no series were found
@@ -213,7 +213,7 @@ class TestSyncSeriesToDatabase:
         from files and the sync function attempts to add them to the DB.
         The actual DB interaction is tested in test_add_to_db_creates_record.
         """
-        from src.server.fastapi_app import _sync_series_to_database
+        from src.server.services.anime_service import sync_series_from_data_files
 
         with tempfile.TemporaryDirectory() as tmp_dir:
             # Create test data files
@@ -241,7 +241,7 @@ class TestSyncSeriesToDatabase:
                  patch('src.core.SeriesApp.SerieScanner'):
                 # The function should return 0 because DB isn't available
                 # but should not crash
-                count = await _sync_series_to_database(tmp_dir, mock_logger)
+                count = await sync_series_from_data_files(tmp_dir, mock_logger)
 
                 # Since no real DB, it will fail gracefully
                 assert isinstance(count, int)
@@ -251,7 +251,7 @@ class TestSyncSeriesToDatabase:
     @pytest.mark.asyncio
     async def test_sync_handles_exceptions_gracefully(self):
         """Test that sync handles exceptions without crashing."""
-        from src.server.fastapi_app import _sync_series_to_database
+        from src.server.services.anime_service import sync_series_from_data_files
 
         mock_logger = Mock()
 
@@ -262,7 +262,7 @@ class TestSyncSeriesToDatabase:
                 'src.core.SeriesApp.SerieList',
                 side_effect=Exception("Test error")
              ):
-            count = await _sync_series_to_database(
+            count = await sync_series_from_data_files(
                 "/fake/path", mock_logger
             )