feat(core): Add database support to SeriesApp (Task 7)

- Added db_session parameter to SeriesApp.__init__()
- Added db_session property and set_db_session() method
- Added init_from_db_async() for async database initialization
- Pass db_session to SerieList and SerieScanner during construction
- Added get_series_app_with_db() dependency for FastAPI endpoints
- All 815 unit tests and 55 API tests pass

src/server/utils/dependencies.py

@@ -65,6 +65,10 @@ def get_series_app() -> SeriesApp:
     Raises:
         HTTPException: If SeriesApp is not initialized or anime directory
                       is not configured
+                      
+    Note:
+        This creates a SeriesApp without database support. For database-
+        backed storage, use get_series_app_with_db() instead.
     """
     global _series_app
     
@@ -103,7 +107,6 @@ def reset_series_app() -> None:
     _series_app = None
 
 
-
 async def get_database_session() -> AsyncGenerator:
     """
     Dependency to get database session.
@@ -166,6 +169,43 @@ async def get_optional_database_session() -> AsyncGenerator:
         yield None
 
 
+async def get_series_app_with_db(
+    db: AsyncSession = Depends(get_optional_database_session),
+) -> SeriesApp:
+    """
+    Dependency to get SeriesApp instance with database support.
+    
+    This creates or returns a SeriesApp instance and injects the
+    database session for database-backed storage.
+    
+    Args:
+        db: Optional database session from dependency injection
+        
+    Returns:
+        SeriesApp: The main application instance with database support
+        
+    Raises:
+        HTTPException: If SeriesApp is not initialized or anime directory
+                      is not configured
+                      
+    Example:
+        @app.post("/api/anime/scan")
+        async def scan_anime(
+            series_app: SeriesApp = Depends(get_series_app_with_db)
+        ):
+            # series_app has db_session configured
+            await series_app.serie_scanner.scan_async()
+    """
+    # Get the base SeriesApp
+    app = get_series_app()
+    
+    # Inject database session if available
+    if db:
+        app.set_db_session(db)
+    
+    return app
+
+
 def get_current_user(
     credentials: Optional[HTTPAuthorizationCredentials] = Depends(
         http_bearer_security