fix: api server installation missing MANIFEST.in file

- Added MANIFEST.in to include webui files
- Removed /webui/ endpoint from lightrag_server.py

MANIFEST.in

@@ -0,0 +1 @@
+recursive-include lightrag/api/webui *

lightrag/api/lightrag_server.py

@@ -410,10 +410,6 @@ def create_app(args):
         name="webui",
     )
 
-    @app.get("/webui/")
-    async def webui_root():
-        return FileResponse(static_dir / "index.html")
-
     return app