- Site model: add waiter_domain and last_seen_local_ip columns
- HeartbeatRequest: accept optional local_ip field from local backend
- HeartbeatResponse: return waiter_domain to local backend
- heartbeat router: persist local_ip on each check-in
- SiteDetailPage: show Public IP / Local IP separately, add Waiter Domain
card with inline edit modal
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>