Add database backups and automatic restore

Daemon job "backup" (online copy, quick_check, rotation), restore of the
newest valid copy when the database cannot be opened, change journal reset
after restore, last_restore in /health, docs and tests.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.dockerignore

@@ -15,3 +15,5 @@ status.json
 *.migrated-*
 collect_request.json
 graphify-out/
+backups/
+last_restore.json