Add monthly offsite restore tests and automatic cleanup

etc/app-backup/app-backup.conf

@@ -48,6 +48,16 @@ MAIL_INCLUDE_LOG_TAIL_LINES=200
 MAIL_SENDMAIL_BIN="/usr/sbin/sendmail"
 MAIL_SEND_TIMEOUT=30
 
+# Monthly offsite restore rehearsal. Prepare a LOCAL MariaDB image matching the
+# production major/minor version before enabling. No automatic image downloads.
+ENABLE_RESTORE_TEST="false"
+RESTORE_TEST_DB_IMAGE=""
+# Components are processed sequentially; fail/clean up if a component will not fit.
+RESTORE_TEST_MAX_WORK_GB=4
+RESTORE_TEST_MIN_FREE_GB=2
+RESTORE_TEST_MAX_AGE_HOURS=72
+RESTORE_TEST_TIMEOUT=39600
+
 ENABLE_WORDPRESS="true"
 WP_DIR="/var/www/html"
 # Nextcloud paths below WP_DIR are automatically excluded (including on restore).