polish: add trap cleanup_restore_rollback to match sibling restore scripts

Final whole-branch review noted alt_mysql_native_backup_restore.sh was the
only one of three consumers of the shared rollback helpers without this
trap, leaving a stale rollback temp file on signal/die().

scripts/da-integration/alt_mysql_native_backup_restore.sh

@@ -309,6 +309,7 @@ if [[ "${BASH_SOURCE[0]}" == "${0}" ]]; then
   [ -r "$COMMON_FILE" ] || die "missing helper: $COMMON_FILE"
   # shellcheck source=../setup/mysql_common.sh
   source "$COMMON_FILE"
+  trap cleanup_restore_rollback INT TERM EXIT
   mysql_load_plugin_settings_file "$SETTINGS_FILE"
   main "$@"
 fi