Raff v1.5.1: Kubernetes firewall enforcement and backup chains

The cluster firewall now actually enforces, and incremental backup chains stop over-deleting.

Security

Kubernetes firewall now actually enforces. Cluster firewalls were applied but not blocking: a default "allow all" rule was silently overriding the secure baseline.

Fixed

Incremental backup chains no longer over-delete. Cleanup could delete the whole chain, including newer points that were still valid.

Snapshot rename and delete errors. Renaming or deleting a snapshot could fail with an internal error.

Long VM names no longer break dialogs. Create Snapshot and Backup/Snapshot dialogs overflowed for very long names.