Rename sync_series_from_data_files to sync_legacy_series_to_db

- Rename function to reflect its legacy status
- Add deprecation warning log on execution
- Update all callers (initialization_service, api/config, fastapi_app)
- Update tests to use new name
- Add deprecation notice to DEVELOPMENT.md

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tests/integration/test_data_file_db_sync.py

@@ -111,17 +111,17 @@ class TestGetAllSeriesFromDataFiles:
 
 
 class TestSyncSeriesToDatabase:
-    """Test sync_series_from_data_files function from anime_service."""
+    """Test sync_legacy_series_to_db function from anime_service."""
 
     @pytest.mark.asyncio
     async def test_sync_with_empty_directory(self):
         """Test sync with empty anime directory."""
-        from src.server.services.anime_service import sync_series_from_data_files
+        from src.server.services.anime_service import sync_legacy_series_to_db
 
         with tempfile.TemporaryDirectory() as tmp_dir:
             with patch('src.core.SeriesApp.Loaders'), \
                  patch('src.core.SeriesApp.SerieScanner'):
-                count = await sync_series_from_data_files(tmp_dir)
+                count = await sync_legacy_series_to_db(tmp_dir)
 
                 assert count == 0
                 # Function should complete successfully with no series
@@ -134,7 +134,7 @@ 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.services.anime_service import sync_series_from_data_files
+        from src.server.services.anime_service import sync_legacy_series_to_db
 
         with tempfile.TemporaryDirectory() as tmp_dir:
             # Create test data files
@@ -160,7 +160,7 @@ 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_from_data_files(tmp_dir)
+                count = await sync_legacy_series_to_db(tmp_dir)
 
                 # Since no real DB, it will fail gracefully
                 # Function returns 0 when DB operations fail
@@ -170,7 +170,7 @@ class TestSyncSeriesToDatabase:
     @pytest.mark.asyncio
     async def test_sync_handles_exceptions_gracefully(self):
         """Test that sync handles exceptions without crashing."""
-        from src.server.services.anime_service import sync_series_from_data_files
+        from src.server.services.anime_service import sync_legacy_series_to_db
 
         # Make SeriesApp raise an exception during initialization
         with patch('src.core.SeriesApp.Loaders'), \
@@ -179,7 +179,7 @@ class TestSyncSeriesToDatabase:
                 'src.core.SeriesApp.SerieList',
                 side_effect=Exception("Test error")
              ):
-            count = await sync_series_from_data_files("/fake/path")
+            count = await sync_legacy_series_to_db("/fake/path")
 
             assert count == 0
             # Function should complete without crashing