fix: hang on win32

Signed-off-by: Dennis Zhuang <killme2008@gmail.com>

Author: killme2008

src/greptimedb_mcp_server/__init__.py

@@ -1,6 +1,9 @@
 import asyncio
 import sys
 
+if sys.platform == "win32":
+    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
+
 if "-m" not in sys.argv:
     from . import server