nixos/rancher: adapt auto deploy test to upstream change to traefik

Upstream changed the default bundled load balancer starting in RKE2 v1.36. This adapts the auto
deploy test accordingly.

From the RKE2 release notes:

Because ingress-nginx was retired upstream as of March 2026, Traefik is now the default for new
clusters starting in v1.36 (existing clusters will keep their current ingress upon upgrade to avoid
breakage). This transition brings the following structural changes:

- Airgapped Environments: The rke2-images-core tarball now contains Traefik images instead of
  ingress-nginx. The standalone rke2-images-traefik tarball has been removed. Users who must continue
  using ingress-nginx will now need to manually provide the rke2-images-ingress-nginx tarball.
- Future Removal: The ingress-nginx chart will not receive any additional updates and will be
  completely removed in v1.37 for community users.
- Prime Customers: Please refer to the official product documentation for specific Prime
  considerations.

nixos/tests/rancher/auto-deploy.nix

@@ -275,9 +275,16 @@ in
             k3s = ''
               machine.wait_until_succeeds("kubectl -n kube-system rollout status deployment traefik")
             '';
-            rke2 = ''
-              machine.wait_until_succeeds("kubectl -n kube-system rollout status daemonset rke2-ingress-nginx-controller")
-            '';
+            rke2 =
+              # Starting from v1.36, RKE2 also uses traefik as default load balancer
+              if lib.versionAtLeast rancherPackage.version "1.36" then
+                ''
+                  machine.wait_until_succeeds("kubectl -n kube-system rollout status daemonset rke2-traefik")
+                ''
+              else
+                ''
+                  machine.wait_until_succeeds("kubectl -n kube-system rollout status daemonset rke2-ingress-nginx-controller")
+                '';
           }
           .${rancherDistro}
         }