ghcr: allow k8up-io images through the docker remote

The k8up operator (deployed via the k8up-system app) and its restic
backup/prune/check jobs both run ghcr.io/k8up-io/k8up, which the
containerd mirror only serves when the image path is allowlisted.

- Add ^k8up-io/ to the ghcr remote patterns

config/remote_docker/ghcr.yaml

@@ -11,6 +11,7 @@ patterns:
   - "^goodtune/ghp"
   - "^home-operations/"
   - "^jellyfin/"
+  - "^k8up-io/"
   - "^netbox-community/"
   - "^onedr0p/"
   - "^open-webui/open-webui"