The app is used internally only and its settings page was German
already. Mails, controller error messages (shown in the form), the
settings section name and the mail sender are now written in German
directly instead of going through IL10N without any translation files.
Nextcloud's own mail footer is requested in German as well.
Ports the standalone due-date cron script into a proper Nextcloud 34
app with a personal-settings UI, per-user workflow configuration
(source/target stack, assigned-user and label filters, email
notification), a TimedJob background runner, and Gitea CI pipelines.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>