fix: add root redirect to /docs and show localhost in serve output

src/server/app.py

@@ -84,6 +84,13 @@ app = FastAPI(
 )
 
 
+@app.get("/")
+def root():
+    """根路径重定向到 API 文档."""
+    from fastapi.responses import RedirectResponse
+    return RedirectResponse(url="/docs")
+
+
 @app.get("/api/v1/health")
 def health():
     return {"status": "ok"}