refactor: remove legacy data file sync functionality

Series now loaded directly from database. Removed:
- sync_legacy_series_to_db() from anime_service.py
- Corresponding sync call after directory update in config.py
- Safety nets in initialization_service.py for missing progress IDs

src/server/services/initialization_service.py

@@ -9,7 +9,6 @@ import structlog
 
 from src.config.settings import settings
 from src.server.database.service import AnimeSeriesService
-from src.server.services.anime_service import sync_legacy_series_to_db
 from src.server.services.setup_service import SetupService
 
 logger = structlog.get_logger(__name__)
@@ -237,14 +236,15 @@ async def _sync_anime_folders(progress_service=None) -> int:
             metadata={"step_id": "series_sync"}
         )
     
-    sync_count = await sync_legacy_series_to_db(settings.anime_directory)
-    logger.info("Data file sync complete. Added %d series.", sync_count)
+    # Legacy sync removed - series are loaded directly from database via _load_series_into_memory
+    sync_count = 0
+    logger.info("Data file sync skipped - series loaded directly from database")
     
     if progress_service:
         await progress_service.update_progress(
             progress_id="series_sync",
             current=75,
-            message=f"Synced {sync_count} series from data files",
+            message=f"Series loaded directly from database",
             metadata={"step_id": "series_sync"}
         )