fix(mcp_admin): add module-level import asyncio to fix 500 in test_mcp_connection (#766 root cause)

backend/python/app/api/admin/mcp_admin.py

@@ -30,6 +30,7 @@ Phase 3.3: Manage MCP servers, discover tools/resources, test connections
 
 
 
+import asyncio
 from fastapi import APIRouter, Depends, HTTPException, Query, Body