3.8.3: Restore administration deletion of archived mails

Archived mails can now be deleted from the administration again. Deletion removes the archive, its attachments, and the stored EML file, while inserts and updates remain restricted to the system scope.

Fixed

• Allowed archive deletion through the administration while retaining write protection for creating and updating archived mails. Deletion controls are governed by the new frosh_mail_archive:delete privilege, and failures now display the API error detail or a fallback message (#164, @shyim).

Full Changelog: 3.8.2...main