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)

apps/api/k8s/base/service.yaml

@@ -8,5 +8,10 @@ spec:
     - port: 80
       targetPort: 4000
       protocol: TCP
+      name: http
+    - port: 9464
+      targetPort: 9464
+      protocol: TCP
+      name: metrics
   selector:
     app: api