Use a stable Restic parent identity and report bytes added by each backup #933

Restic workers have ephemeral pod names. Restic groups parent snapshots by hostname and paths by default. A stable source identity allows a later backup to avoid rereading unchanged files. Operators also need the number of bytes this run added to the repository.

Implementation and verification

1. Derive a stable Restic host argument from the GameServer identity bound to this backup. Test repeated workers, same-named servers in shared repositories, server recreation and restoration of an old snapshot by ID.
2. Record packed bytes added as an optional per-run status field. Preserve a measured zero and leave missing or unsupported metrics absent. Carry the field through generated CRDs and both backup views.
3. Display logical size and bytes added separately, including for historical and CSI backups. Verify the parent decision and restore with Restic and exercise the parser and UI on mixed histories. Coordinate with fix(backups): distinguish flushed saves from verified write freezes #907 when integrating the worker changes.