feat(llm): add auth for fastapi and gradio

[ChenZiHong-Gavin]

1. add auth to gradio(using auth provided by gradio) auth – If provided, username and password (or list of username-password tuples) required to access the gradio app. Can also provide function that takes username and password and returns True if valid login. refer: https://www.gradio.app/main/docs/gradio/blocks
2. add auth to fastapi(using APIRouter) refer: https://fastapi.tiangolo.com/reference/apirouter/#fastapi.APIRouter