Send a body with the 400 from shell/trash-item

[sadiqk2]

try {
    await shell.trashItem(path);
    res.sendStatus(200);
} catch {
    res.status(400).json();
}

res.json() with no argument throws in express, so the caught failure becomes an unhandled error inside the handler rather than the 400 the code intends. The caller sees a hung or 500 request instead of a clean failure.

Passing the message through also means the caller learns why — trashing fails for ordinary reasons (a permission problem, a path on a volume without a trash) and PHP-side Shell::trash() currently has no way to report which.

[sadiqk2]

@simonhamp kindly review