#5823 "Check a backup: compare what it would restore with what is in place, without restoring". - steward/backup/check.py: pg_restore writes the backup's rows as COPY text with no database involved. The rows in place go out through COPY in the same form. Tables are compared on their primary keys, over the columns both sides have, and grouped by area. - Sealed values are opened with each side's own key and compared as plaintext digests, so a secret sealed twice still matches. They are never shown. A backup whose key can't open its own secrets fails the check. - What Steward records as it runs (last-seen times, a schedule's last run, backup history, scraped UniFi fields) is left out of the comparison: contents.ACTIVITY, STATE_SETTINGS and HAND_SET_ONLY. - Settings → Backups: - a Check button on each sent backup, which fetches it from the bucket (new s3.get_file); - "Check a file" to upload one, with the size limit raised before the CSRF check reads the form; - a results page. - Each backup Steward sends checks itself once written, and its history row says how that went. - New CLI command `steward check-backup FILE`. CI's image smoke step checks a real backup against its source and expects a match. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>