feat(config): Refactor configuration management

- Optimize JWT Auth module to load configuration via `global_args`.
- Decouple configuration-related code from `utils_api.py`, and add a new `config.py` file for unified configuration management.
- Adjust configuration import in `lightrag_server.py`, `auth.py`, and `document_routes.py` to be introduced through `global_args`.

env.example

@@ -160,7 +160,9 @@ REDIS_URI=redis://localhost:6379
 ### For JWT Auth
 AUTH_ACCOUNTS='admin:admin123,user1:pass456'     # username:password,username:password
 TOKEN_SECRET=Your-Key-For-LightRAG-API-Server    # JWT key
-TOKEN_EXPIRE_HOURS=4                             # expire duration
+#TOKEN_EXPIRE_HOURS=4                             # Expire duration, default 4
+#GUEST_TOKEN_EXPIRE_HOURS=2                       # Guest expire duration, default 2
+#JWT_ALGORITHM=HS256                              # JWT encode algorithm, default HS256
 
 ### API-Key to access LightRAG Server API
 # LIGHTRAG_API_KEY=your-secure-api-key-here