admin: backup logs via parameters.php, nextcloud secondary backup

- surface backup/cleanup cron logs + backup freshness status
- email xamxam@erg.be when SQLite backups go stale (backup watchdog)
- sync SQLite snapshots to Nextcloud WebDAV + remote-freshness watchdog
- precise retention pruning, manual sync in check recipe, and Nextcloud-sync docs

deploy/xamxam-backup.cron

@@ -6,3 +6,9 @@
 
 # Daily snapshot at 2am — kept 90 days
 0  2  *  *  *  www-data  RETENTION_DAYS=90 /usr/local/bin/backup-sqlite.sh >> /var/log/xamxam-backup-$(date +\%Y-\%m-\%d).log 2>&1
+
+# Push the latest snapshot to Nextcloud WebDAV (daily, after the 2am snapshot)
+20  2  *  *  *  www-data  php /usr/local/bin/nextcloud-sync.php >> /var/log/xamxam-backup-$(date +\%Y-\%m-\%d).log 2>&1
+
+# Backup watchdog — email xamxam@erg.be when backups go stale (runs 15 min after the hourly snapshot)
+15 *  *  *  *  www-data  php /usr/local/bin/backup-watchdog.php >> /var/log/xamxam-backup-$(date +\%Y-\%m-\%d).log 2>&1