Better Mailbox

Changelog 0.4.0 BETA

- Added a new open-mail detail view inside BetterMailbox.
- Double-clicking an inbox message now opens the letter inside the custom mailbox UI.
- Added a dedicated reading layout showing subject, sender, expiration time, message body, attached gold, and attachments.
- Added manual attachment looting directly from the open-mail view.
- Added a Reply button in the open-mail view.
- Added a Back button to return from the mail view to the normal inbox.
- Reply now opens the custom send panel and prefills the recipient and reply subject.
- Added new localized strings for the open-mail view and reply flow.
- Completed localization support for all selectable languages in the options menu:
  English, German, French, and Russian.
- Added missing translations for older UI elements in supported languages where they were incomplete.
- Cleaned up and rebuilt the locale file structure for more consistent language handling.
- Fixed German special-character text such as Zurück and Anhänge.
- Updated the addon version to 0.4.0 BETA.