fix: persist service host port; demo-data scope for telemetry

Public URLs were ephemeral: every restart/redeploy rebound a random host
port, so endpoint links rotted. Persist published_port on the service and
prefer it for replica 0 on create. If the port is taken, fall back to
ephemeral and repersist the new assignment. Post-start the binding is
verified — Docker Desktop accepts a conflicting publish silently, which
previously left services running with no endpoint at all.

demo-data.ts gains the required scope field for HostMonitoring (CI fix).

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/frontend/src/lib/demo-data.ts

@@ -456,6 +456,7 @@ export const demoHostMonitoring: HostMonitoring = {
   uptimeSeconds: 1_828_800,
   dockerAvailable: true,
   docker: { containers: 11, images: 34, driver: 'overlay2', server: '27.3.1' },
+  scope: 'host',
   collectedAt: new Date().toISOString(),
 };