Scrape the Kong gateways

Every dataplane pod the Kong operator creates declares a container port named
`metrics` (8100) and carries the gateway-name label, so discovery keys off
those rather than an annotation — the operator owns that pod template, not us,
and adding annotations there would mean editing the shared dataplane template
and restarting every gateway.

Keeping on the port NAME rather than a number also drops the init containers,
which declare no port at all.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

k8s/prometheus/prometheus.yaml

@@ -175,3 +175,35 @@ scrape_configs:
         target_label: container
       - target_label: service
         replacement: librechat
+
+  # --- Kong gateways ------------------------------------------------------
+  # Every dataplane pod the Kong operator creates declares a container port
+  # named `metrics` (8100) and carries the gateway-name label, so no
+  # annotation is needed on the pods themselves — which matters because the
+  # operator owns that pod template, not us. Keeping on the port NAME rather
+  # than a number also drops the init containers, which declare no port.
+  #
+  # The RED series (kong_http_requests_total, kong_*_latency_ms,
+  # kong_bandwidth_bytes) only appear once the gateway has the `prometheus`
+  # KongPlugin bound; without it the endpoint still answers, but with node
+  # and shared-dict metrics only.
+  - job_name: kong-gateways
+    kubernetes_sd_configs:
+      - role: pod
+    relabel_configs:
+      - source_labels: [__meta_kubernetes_pod_label_gateway_networking_k8s_io_gateway_name]
+        action: keep
+        regex: .+
+      - source_labels: [__meta_kubernetes_pod_container_port_name]
+        action: keep
+        regex: metrics
+      - source_labels: [__meta_kubernetes_pod_label_gateway_networking_k8s_io_gateway_name]
+        target_label: gateway
+      - source_labels: [__meta_kubernetes_namespace]
+        target_label: namespace
+      - source_labels: [__meta_kubernetes_pod_name]
+        target_label: pod
+      - source_labels: [__meta_kubernetes_pod_container_name]
+        target_label: container
+      - source_labels: [__meta_kubernetes_pod_node_name]
+        target_label: node