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).

Generated with [Devin](https://devin.ai)

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

app/backend/internal/deployment/engine.go

@@ -59,6 +59,9 @@ type ServiceConfig struct {
 	Domain string `json:"domain,omitempty"`
 	// HealthPath is an HTTP path probed on PublicPort for container health.
 	HealthPath string `json:"health_path,omitempty"`
+	// PublishedPort is the host port bound by the previous deployment; replica 0
+	// reuses it so public URLs survive restarts. 0 = pick ephemeral.
+	PublishedPort int32 `json:"published_port,omitempty"`
 }
 
 type PortMapping struct {
@@ -315,6 +318,7 @@ func (de *DeploymentEngine) deployService(ctx context.Context, deployment *Deplo
 		Env:           cfg.Environment,
 		Replicas:      cfg.Replicas,
 		Port:          cfg.PublicPort,
+		PublishedPort: cfg.PublishedPort,
 		Domain:        cfg.Domain,
 		HealthPath:    cfg.HealthPath,
 		RestartPolicy: cfg.RestartPolicy,