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/schemas/site.py

@@ -14,6 +14,7 @@ class SiteUpdate(BaseModel):
     owner_name: str | None = None
     contact_email: str | None = None
     license_expires_at: datetime | None = None
+    waiter_domain: str | None = None
 
 
 class SiteOut(BaseModel):
@@ -29,6 +30,8 @@ class SiteOut(BaseModel):
     created_at: datetime
     last_seen_at: datetime | None
     last_seen_ip: str | None
+    last_seen_local_ip: str | None
+    waiter_domain: str | None
 
     model_config = {"from_attributes": True}
 
@@ -44,6 +47,7 @@ class LockRequest(BaseModel):
 class HeartbeatRequest(BaseModel):
     version: str = "1.0.0"
     uptime_seconds: int = 0
+    local_ip: str | None = None
 
 
 class HeartbeatResponse(BaseModel):
@@ -51,3 +55,5 @@ class HeartbeatResponse(BaseModel):
     locked: bool
     lock_reason: str | None
     expires_at: datetime
+    latest_version: str | None = None
+    waiter_domain: str | None = None