Add observability stack: ServiceMonitors, Tempo, OTel API instrumentation, dashboards

- Add ServiceMonitors for Traefik, ArgoCD, and Longhorn
- Enable cert-manager ServiceMonitor via helm values
- Deploy Grafana Tempo for distributed tracing (single-binary, Longhorn PVC)
- Add Tempo datasource with trace-to-logs and trace-to-metrics correlation
- Instrument API with OpenTelemetry SDK (Prometheus metrics + OTLP traces)
- Replace console.log with pino structured logging + pino-http middleware
- Add Grafana dashboards for Traefik, API overview, and PostgreSQL (CNPG)

infra/kubernetes/platform/cert-manager/application.yaml

@@ -15,6 +15,9 @@ spec:
       valuesObject:
         crds:
           enabled: true
+        prometheus:
+          servicemonitor:
+            enabled: true
   destination:
     server: https://kubernetes.default.svc
     namespace: cert-manager