Adds scripts/backup.sh — atomic SQLite .backup + hard-linked point-in-time
content snapshots, daily (7) + monthly (12) retention, and an error log.
Env-configurable (SCREENTINKER_DIR/BACKUP_DIR/DB/UPLOADS/*_KEEP*) so any
self-hoster can use it; defaults target a /opt/screentinker install.
Hardens two real failure modes found in production:
- Content snapshots EXCLUDE uploads/screenshots/ and use rsync --link-dest
instead of cp -al. The per-device *_latest.jpg screenshots are rewritten
24/7; cp -al aborts when a file mutates mid-copy and the prior script
swallowed the error with 2>/dev/null, silently breaking content snapshots
for ~8 weeks. rsync --link-dest hard-links unchanged files but tolerates
in-flight changes; errors now go to backup.log.
- Retention sorts by NAME, not mtime: rsync -a / cp -al preserve the source
dir's (frozen) mtime, so ls -dt treated fresh snapshots as oldest and pruned
them. The timestamp is in the dir name, so name-sort is chronological.
README Backups section documents the cron setup + env knobs. Verified on prod.
