Final-review gaps in the system-config backup:
1. Scheduled (cron) backups skipped it — backupScheduleEnabledApps only queued
per-app backups, so the daily schedule never refreshed the system config (and
thus the backup-location creds could go stale). Now it queues a
`libreportal backup system` task (or runs inline on terminal-only installs),
and skips the reproducible libreportal app for consistency with backupAllApps.
2. No retention on system snapshots — they bypass backupAppStart's per-app forget,
so they accumulated unbounded. Add resticForgetSystem (tag system=config,
respects append-only + the same keep-* policy) + engineForgetSystem dispatcher;
backupSystemConfig now applies retention across all locations after snapshotting.
Verified with stubs: backupSystemConfig snapshots AND prunes on every location;
engineForgetSystem pairs with resticForgetSystem; scheduled createTaskFile call
matches the existing 3-arg signature.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Signed-off-by: librelad <librelad@digitalangels.vip>
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