## 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
