Use Transport.__members__ for Python 3.11 compat

Author: sd2k

src/mcp_grafana/__init__.py

@@ -54,7 +54,7 @@ def run(self, transport: Literal["http", "stdio", "sse"] = "stdio") -> None:
         Args:
             transport: Transport protocol to use ("stdio" or "sse")
         """
-        if transport not in Transport:
+        if transport not in Transport.__members__:
             raise ValueError(f"Unknown transport: {transport}")
 
         if transport == "stdio":