refactor: restructure core→server, split large entity files into database module

- Move src/core/ → src/server/
- Split SerieList.py (531 lines) and series.py (414 lines) into src/server/database/
- Add database/models.py for SQLAlchemy models
- Update all test imports to reflect new structure
- Remove deprecated test files (test_serie_class.py, test_serie_folder_with_year.py)

src/cli/nfo_cli.py

@@ -120,7 +120,7 @@ async def check_nfo_status():
     logger.info("Anime Directory: %s", settings.anime_directory)
 
     # Create series list (no NFO service needed for status check)
-    from src.core.entities.SerieList import SerieList
+    from src.server.database.SerieList import SerieList
     serie_list = SerieList(settings.anime_directory)
     all_series = serie_list.get_all()