Convert RKE2 registries to template, disable default endpoints (#474)

## Summary
- Replace static `registries.yaml` with EPP template driven by `rke2::registries` hash
- Add `disable-default-registry-endpoint: true` to all mirrors — RKE2 will only use artifactapi and never fall back to upstream registries
- Registry configuration now fully managed via hiera data (`roles/infra/k8s.yaml`)

Reviewed-on: #474
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

hieradata/roles/infra/k8s.yaml

@@ -55,6 +55,18 @@ rke2::registries:
     rewrite:
       "^(.*)$": "gcr/$1"
     disable-default-registry-endpoint: true
+  docker.litellm.ai:
+    endpoint:
+      - "https://artifactapi.k8s.syd1.au.unkin.net"
+    rewrite:
+      "^(.*)$": "litellm/$1"
+    disable-default-registry-endpoint: true
+  public.ecr.aws:
+    endpoint:
+      - "https://artifactapi.k8s.syd1.au.unkin.net"
+    rewrite:
+      "^(.*)$": "ecr-public/$1"
+    disable-default-registry-endpoint: true
 rke2::config_hash:
   bind-address: "%{hiera('networking_loopback0_ip')}"
   node-ip: "%{hiera('networking_loopback0_ip')}"