feat: waiter domain + local IP tracking

- 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>

cloud_backend/routers/heartbeat.py

@@ -3,6 +3,7 @@ from fastapi import APIRouter, Depends, HTTPException, Header, Request, status
 from passlib.context import CryptContext
 from sqlalchemy.orm import Session
 
+from config import settings
 from database import get_db
 from models.site import Site
 from schemas.site import HeartbeatRequest, HeartbeatResponse
@@ -26,6 +27,8 @@ def heartbeat(
     now = datetime.now(timezone.utc)
     site.last_seen_at = now
     site.last_seen_ip = request.client.host if request.client else None
+    if body.local_ip:
+        site.last_seen_local_ip = body.local_ip
     db.commit()
 
     licensed = site.is_active and (site.license_expires_at.replace(tzinfo=timezone.utc) > now)
@@ -34,4 +37,6 @@ def heartbeat(
         locked=site.is_locked,
         lock_reason=site.lock_reason,
         expires_at=site.license_expires_at,
+        latest_version=settings.LATEST_VERSION,
+        waiter_domain=site.waiter_domain,
     )