A backup killed mid-run leaves a lock behind; the next night's backup
still works (non-exclusive) but forget fails and the run reports
rc=1 for ever. restic-maintenance.sh already did this.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
First cron run (2026-08-28 05:00) failed with 'restic: command not
found'; interactive shells had /usr/local/bin, cron does not.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>