Remove migration code and alembic dependency

src/server/api/auth.py

@@ -31,7 +31,6 @@ async def setup_auth(req: SetupRequest):
     
     This endpoint also initializes the configuration with default values
     and saves the anime directory and master password hash.
-    If anime_directory is provided, runs migration for existing data files.
     """
     if auth_service.is_configured():
         raise HTTPException(

src/server/api/config.py

@@ -214,14 +214,14 @@ def update_advanced_config(
 async def update_directory(
     directory_config: Dict[str, str], auth: dict = Depends(require_auth)
 ) -> Dict[str, Any]:
-    """Update anime directory configuration and run migration.
+    """Update anime directory configuration.
 
     Args:
         directory_config: Dictionary with 'directory' key
         auth: Authentication token (required)
 
     Returns:
-        Success message with optional migration results
+        Success message
     """
     try:
         directory = directory_config.get("directory")