feat(api): add Kong RED metrics for LLM routes

Cluster-wide prometheus KongClusterPlugin (kong-metrics.yaml) +
chart-native ServiceMonitor (kong-values.yaml) expose
kong_http_requests_total/kong_latency_bucket/kong_bandwidth_bytes for
every route, LLM and otherwise. Dashboard filters to route=~"llm-.*"
for request rate, error rate, p95 upstream latency, and bandwidth.
Token-count metrics still need ai-proxy-advanced (Enterprise-only);
not attempted.

k8s/apps/api/kong-values.yaml

@@ -118,6 +118,16 @@ podDisruptionBudget:
   enabled: true
   minAvailable: 1
 
+# Status listener (metrics/health) is on by default at :8100 (chart default,
+# verified via `helm show values`). This just wires the ServiceMonitor the
+# chart already knows how to generate for it, so kong_http_requests_total /
+# kong_latency_* / kong_bandwidth_bytes land in Prometheus. Paired with the
+# cluster-wide `prometheus` KongClusterPlugin in kong-metrics.yaml.
+serviceMonitor:
+  enabled: true
+  labels:
+    release: kube-prometheus-stack
+
 # Spread the two replicas across nodes; `ScheduleAnyway` so a single-node
 # situation degrades to co-location instead of leaving a pod Pending.
 topologySpreadConstraints: