feat(puppet): migrate puppetdb Ingress to Gateway API (#131)

## Summary

- Replace `Ingress` (nginx) with `Gateway` + `HTTPRoute` using `traefik-internal` GatewayClass
- TLS terminated at the Gateway listener; cert-manager provisions the certificate via `vault-issuer`
- external-dns annotations moved to the Gateway
- `ingress_puppetboard.yaml` is unchanged in this PR (separate PR)

## Test plan

- [ ] ArgoCD syncs the puppet app cleanly
- [ ] cert-manager issues the `puppetdb-tls` certificate
- [ ] external-dns creates the DNS record
- [ ] `https://puppetdb.k8s.syd1.au.unkin.net` is reachable

Reviewed-on: #131

apps/base/puppet/gateway_puppetdb.yaml

@@ -0,0 +1,33 @@
+---
+apiVersion: gateway.networking.k8s.io/v1
+kind: Gateway
+metadata:
+  annotations:
+    cert-manager.io/cluster-issuer: vault-issuer
+    cert-manager.io/common-name: puppetdb.k8s.syd1.au.unkin.net
+    cert-manager.io/private-key-size: "4096"
+    external-dns.alpha.kubernetes.io/hostname: puppetdb.k8s.syd1.au.unkin.net
+    external-dns.alpha.kubernetes.io/target: 198.18.200.4
+  labels:
+    traefik.io/instance: internal
+    app.kubernetes.io/component: puppetdb
+    app.kubernetes.io/instance: puppetserver
+    app.kubernetes.io/name: puppetserver
+    app.kubernetes.io/version: 8.8.0
+  name: puppetdb
+  namespace: puppet
+spec:
+  gatewayClassName: traefik-internal
+  listeners:
+    - allowedRoutes:
+        namespaces:
+          from: Same
+      hostname: puppetdb.k8s.syd1.au.unkin.net
+      name: https
+      port: 443
+      protocol: HTTPS
+      tls:
+        certificateRefs:
+          - kind: Secret
+            name: puppetdb-tls
+        mode: Terminate