**Motivations:**
- Export Signet and mining wallet backups to git with only 2 versions kept
- Document and add backup/restore scripts for signet and mining wallet
**Correctifs:**
- Backup-to-git uses SSH URL for passwordless cron; copy timestamped files only; prune to 2 versions; remove *-latest from backup repo
**Evolutions:**
- data/backup-to-git-cron.sh: daily export to git.4nkweb.com/4nk/backup
- save-signet-datadir-backup.sh, restore-signet-from-backup.sh, export-mining-wallet.sh, import-mining-wallet.sh
- features/backup-to-git-daily-cron.md, docs/MAINTENANCE.md backup section
- .gitignore: data/backup-to-git.log
**Pages affectées:**
- .gitignore, data/backup-to-git-cron.sh, docs/MAINTENANCE.md, features/backup-to-git-daily-cron.md
- save-signet-datadir-backup.sh, restore-signet-from-backup.sh, export-mining-wallet.sh, import-mining-wallet.sh
- Plus autres fichiers modifiés ou non suivis déjà présents dans le working tree
