chore: 添加 db-backup/ 目录到 gitignore

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Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

.gitignore

@@ -54,6 +54,7 @@ allin_system-master/
 # database backups
 backups/
 backups-prd/
+db-backup/
 scripts/time_logger.sh
 loop.txt
 .nfs*