fix: update root_path default value to empty string

Author: LiangYang666

src/mcp/server/fastmcp/server.py

@@ -89,7 +89,7 @@ class Settings(BaseSettings, Generic[LifespanResultT]):
     # HTTP settings
     host: str = "0.0.0.0"
     port: int = 8000
-    root_path: str = "/" # root path, same with root_path in uvicorn config, for sse or streamable http
+    root_path: str = "" # root path, same with root_path in uvicorn config, for sse or streamable http
     mount_path: str = "/"  # Mount path (e.g. "/github", defaults to root path)
     sse_path: str = "/sse"
     message_path: str = "/messages/"