feat(litellm): migrate Ingress to Gateway API

Replace nginx Ingress with Gateway + HTTPRoute using the traefik-internal
GatewayClass. TLS is terminated at the Gateway listener via cert-manager.

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: /