feat(monitoring): wire up full LGTM observability stack

- Prometheus: discover ServiceMonitors/PodMonitors in all namespaces,
  enable remote write receiver for Tempo metrics generator
- Tempo: enable metrics generator (service-graphs + span-metrics)
  with remote write to Prometheus
- Loki: add Grafana Alloy DaemonSet to ship container logs
- Grafana: enable dashboard sidecar, add Pingora/Loki/Tempo/OpenBao
  dashboards, add stable UIDs and cross-linking between datasources
  (Loki↔Tempo derived fields, traces→logs, traces→metrics, service map)
- Linkerd: enable proxy tracing to Alloy OTLP collector, point
  linkerd-viz at existing Prometheus instead of deploying its own
- Pingora: add OTLP rollout plan (endpoint commented out until proxy
  telemetry panic fix is deployed and Alloy is verified healthy)

base/mesh/kustomization.yaml

@@ -29,9 +29,11 @@ helmCharts:
     version: "2025.12.3"
     releaseName: linkerd-control-plane
     namespace: mesh
+    valuesFile: linkerd-control-plane-values.yaml
 
   - name: linkerd-viz
     repo: https://helm.linkerd.io/edge
     version: "2026.1.4"
     releaseName: linkerd-viz
     namespace: mesh
+    valuesFile: linkerd-viz-values.yaml