fix: 修复 /auth/config.js 端点缺少 g_config 导入的问题

app/main.py

@@ -121,6 +121,7 @@ def create_app() -> FastAPI:
     @app.get("/auth/config.js", tags=["Auth"])
     async def get_frontend_config():
         """Provide API key to built-in frontend."""
+        from app.utils import g_config
         config_js = f"""
         window.GEMINI_CONFIG = {{
             API_KEY: "{g_config.server.api_key or ''}"