Backup/restore now pass the target database via PGDATABASE instead of
a CLI/positional argument, so the XSS regression test's check against
the displayed command string could never find the db name (escaped or
not) and always failed. Point Backup's check at the message field,
where the db name is still interpolated; for Restore, where the db
name no longer surfaces anywhere (command shows an always-empty
--dbname, message omits it entirely), assert its absence instead.
f09776c22d