fix(svc-registry-docker): exclude the registry volume from backups

The file's own header already claims the volume is backup-disabled, but nothing declared it, so the cluster's local registry - a compressed copy of every image built for the closure - went into the backup at 6185 MB. The NFS dedup path cannot exclude it either, because it short-circuits on placement: manager, and the image-level escape hatch compares against a ref the registry container cannot run under.

That is what tipped the swarm DR drill's disk precondition: 16397 MB required against 14825 MB free. Removing the bytes helps twice over, since capture and free space share one filesystem, and the guard passes from 786 MB saved onwards.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

roles/svc-registry-docker/meta/volumes.yml

@@ -3,6 +3,7 @@
 data:
   type: volume
   name: docker_registry_data
+  backup: false
   mounts:
     - service: docker
       target: /var/lib/registry