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/server/api/anime.py

@@ -8,8 +8,8 @@ from pydantic import BaseModel, Field
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from src.config.settings import settings
-from src.core.entities.series import Serie
-from src.core.utils.key_utils import generate_key_from_folder, is_valid_key
+from src.server.database.models import AnimeSeries
+from src.server.utils.key_utils import generate_key_from_folder, is_valid_key
 from src.server.database.service import AnimeSeriesService
 from src.server.exceptions import (
     BadRequestError,
@@ -896,18 +896,18 @@ async def add_series(
         
         # Step D: Add to SerieList (in-memory only, no folder creation)
         if series_app and hasattr(series_app, "list"):
-            serie = Serie(
+            from src.server.database.models import AnimeSeries
+            anime = AnimeSeries(
                 key=key,
                 name=name,
                 site="aniworld.to",
                 folder=folder,
-                episodeDict={},
                 year=year
             )
-            
+
             # Add to in-memory cache without creating folder on disk
             if hasattr(series_app.list, 'keyDict'):
-                series_app.list.keyDict[key] = serie
+                series_app.list.keyDict[key] = anime
                 logger.info(
                     "Added series to in-memory cache: %s (key=%s, folder=%s, year=%s)",
                     name,