feat(litellm): migrate Ingress to Gateway API (#134)

## 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

## Test plan

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

Reviewed-on: #134

apps/base/litellm/gateway.yaml

@@ -0,0 +1,29 @@
+---
+apiVersion: gateway.networking.k8s.io/v1
+kind: Gateway
+metadata:
+  labels:
+    traefik.io/instance: internal
+  annotations:
+    cert-manager.io/cluster-issuer: vault-issuer
+    cert-manager.io/common-name: litellm.k8s.syd1.au.unkin.net
+    cert-manager.io/private-key-size: "4096"
+    external-dns.alpha.kubernetes.io/hostname: litellm.k8s.syd1.au.unkin.net
+    external-dns.alpha.kubernetes.io/target: 198.18.200.4
+  name: litellm
+  namespace: litellm
+spec:
+  gatewayClassName: traefik-internal
+  listeners:
+    - allowedRoutes:
+        namespaces:
+          from: Same
+      hostname: litellm.k8s.syd1.au.unkin.net
+      name: https
+      port: 443
+      protocol: HTTPS
+      tls:
+        certificateRefs:
+          - kind: Secret
+            name: litellm-tls
+        mode: Terminate

apps/base/litellm/httproute.yaml

@@ -0,0 +1,20 @@
+---
+apiVersion: gateway.networking.k8s.io/v1
+kind: HTTPRoute
+metadata:
+  name: litellm
+  namespace: litellm
+spec:
+  hostnames:
+    - litellm.k8s.syd1.au.unkin.net
+  parentRefs:
+    - name: litellm
+      sectionName: https
+  rules:
+    - backendRefs:
+        - name: litellm
+          port: 4000
+      matches:
+        - path:
+            type: PathPrefix
+            value: /

apps/base/litellm/ingress.yaml

@@ -1,29 +0,0 @@
----
-apiVersion: networking.k8s.io/v1
-kind: Ingress
-metadata:
-  annotations:
-    kubernetes.io/ingress.class: nginx
-    external-dns.alpha.kubernetes.io/hostname: litellm.k8s.syd1.au.unkin.net
-    external-dns.alpha.kubernetes.io/target: 198.18.200.0
-    cert-manager.io/cluster-issuer: vault-issuer
-    cert-manager.io/common-name: litellm.k8s.syd1.au.unkin.net
-    cert-manager.io/private-key-size: "4096"
-  name: litellm
-  namespace: litellm
-spec:
-  rules:
-    - host: litellm.k8s.syd1.au.unkin.net
-      http:
-        paths:
-          - backend:
-              service:
-                name: litellm
-                port:
-                  number: 4000
-            path: /
-            pathType: Prefix
-  tls:
-    - hosts:
-        - litellm.k8s.syd1.au.unkin.net
-      secretName: litellm-tls

apps/base/litellm/kustomization.yaml

@@ -7,7 +7,8 @@ resources:
   - cnpg_pooler.yaml
   - deployment.yaml
   - hpa.yaml
-  - ingress.yaml
+  - gateway.yaml
+  - httproute.yaml
   - namespace.yaml
   - redis-deployment.yaml
   - redis-pvc.yaml