Fix Issue 7: Enforce repository pattern consistency

- Added 5 new service methods for complete database coverage:
  * get_series_without_nfo()
  * count_all()
  * count_with_nfo()
  * count_with_tmdb_id()
  * count_with_tvdb_id()

- Eliminated all direct database queries from business logic:
  * series_manager_service.py - now uses AnimeSeriesService
  * anime_service.py - now uses service layer methods

- Documented architecture decision in ARCHITECTURE.md:
  * Service layer IS the repository layer
  * No direct SQLAlchemy queries allowed outside service layer

- All database access must go through service methods
- 1449 tests passing, repository pattern enforced

src/core/services/series_manager_service.py

@@ -132,45 +132,45 @@ class SeriesManagerService:
                 ids = self.nfo_service.parse_nfo_ids(nfo_path)
                 
                 if ids["tmdb_id"] or ids["tvdb_id"]:
-                    # Create database session for this task
+                    # Update database using service layer
                     from datetime import datetime, timezone
 
-                    from sqlalchemy import select
-
                     from src.server.database.connection import get_db_session
-                    from src.server.database.models import AnimeSeries
+                    from src.server.database.service import AnimeSeriesService
                     
                     async with get_db_session() as db:
-                        result = await db.execute(
-                            select(AnimeSeries).filter(
-                                AnimeSeries.key == serie_key
-                            )
-                        )
-                        series = result.scalars().first()
+                        series = await AnimeSeriesService.get_by_key(db, serie_key)
                         
                         if series:
                             now = datetime.now(timezone.utc)
-                            series.has_nfo = True
+                            
+                            # Prepare update fields
+                            update_fields = {
+                                "has_nfo": True,
+                                "nfo_updated_at": now,
+                            }
                             
                             if series.nfo_created_at is None:
-                                series.nfo_created_at = now
-                            series.nfo_updated_at = now
+                                update_fields["nfo_created_at"] = now
                             
                             if ids["tmdb_id"] is not None:
-                                series.tmdb_id = ids["tmdb_id"]
+                                update_fields["tmdb_id"] = ids["tmdb_id"]
                                 logger.debug(
                                     f"Updated TMDB ID for '{serie_name}': "
                                     f"{ids['tmdb_id']}"
                                 )
                             
                             if ids["tvdb_id"] is not None:
-                                series.tvdb_id = ids["tvdb_id"]
+                                update_fields["tvdb_id"] = ids["tvdb_id"]
                                 logger.debug(
                                     f"Updated TVDB ID for '{serie_name}': "
                                     f"{ids['tvdb_id']}"
                                 )
                             
+                            # Use service layer for update
+                            await AnimeSeriesService.update(db, series.id, **update_fields)
                             await db.commit()
+                            
                             logger.info(
                                 f"Updated database with IDs from NFO for "
                                 f"'{serie_name}' - TMDB: {ids['tmdb_id']}, "