feat(monitoring): add LLM Frontend Grafana dashboard

Resources (CPU/mem/restarts) + Loki logs across llm-serving, agent-pod,
and api (Kong) namespaces, mirroring the svc-*.yaml dashboard pattern.
No request-rate/latency/token panels yet -- no ServiceMonitor exists
for Kong or the KServe predictors, so there's no metric to query.

k8s/infra/monitoring/kustomization.yaml

@@ -19,6 +19,7 @@ resources:
   - dashboards/control-plane-logs.yaml
   - dashboards/hardware-overview.yaml
   - dashboards/kube-controller-health.yaml
+  - dashboards/llm-frontend.yaml
   - dashboards/service-availability.yaml
   - dashboards/service-golden-signals.yaml
   - dashboards/service-internals.yaml