Add Gunicorn support for production deployment of LightRAG server

- Move gunicorn startup an config files to api package
- Create new CLI entry point for Gunicorn mode

setup.py

@@ -112,6 +112,7 @@ setuptools.setup(
     entry_points={
         "console_scripts": [
             "lightrag-server=lightrag.api.lightrag_server:main [api]",
+            "lightrag-gunicorn=lightrag.api.run_with_gunicorn:main [api]",
             "lightrag-viewer=lightrag.tools.lightrag_visualizer.graph_visualizer:main [tools]",
         ],
     },