feat: add agent zones

agents/windows/config.example.json

@@ -2,6 +2,7 @@
   "hub_url": "https://minerops.example.invalid",
   "agent_id": "replace-with-agent-id",
   "site_id": "00000000-0000-0000-0000-000000000000",
+  "agent_zone_id": "00000000-0000-0000-0000-000000000000",
   "site_name": "Example Site",
   "agent_secret": "replace-with-agent-secret",
   "poll_interval_seconds": 120,