fix: load series from database on every startup

- Add _load_series_from_db call in lifespan startup
- Series now loaded into memory on every app start
- Fixes empty anime list issue (GET /api/anime)

src/server/fastapi_app.py

@@ -219,6 +219,11 @@ async def lifespan(_application: FastAPI):
                 from src.server.utils.dependencies import get_anime_service
                 anime_service = get_anime_service()
                 
+                # Always load series from database into memory on startup
+                logger.info("Loading series from database into memory...")
+                await anime_service._load_series_from_db()
+                logger.info("Series loaded from database into memory")
+                
                 # Run NFO scan only on first run (if configured)
                 await perform_nfo_scan_if_needed()