The panel boots the DB with `new DatabaseHandler()` and no arguments, so $host
is null and the real credentials are resolved by the bundled XC_VM extension in
db_connect() — dbhost is never used on that path. A strict
`normalizeHost(string $rHost)` hint turned that normal null into a fatal
TypeError at bootstrap (initDatabase → __construct → normalizeHost), taking down
console.php / cron boot:
Database::normalizeHost(): Argument #1 ($rHost) must be of type string,
null given, called in .../Database.php on line 53
Make normalizeHost accept and pass through null (?string → ?string), restoring
the pre-typing behaviour; the explicit-credentials path (db_explicit_connect)
still passes a real string. Also make the constructor's implicitly-nullable
`string $x = null` params explicitly `?string` (same root cause, no behaviour
change, and avoids the PHP 8.4 implicit-nullable deprecation).
Add DatabaseHostTest as a regression (reflection on a constructor-less instance,
since the class needs the XC_VM extension to instantiate).
