Enable AI in mail (& add to delegated settings)

[seriAlizations]

TODO

• merge IONOS(fix): enable delegated settings and AI ncw-mail#15
• merge Add groupware to delegated settings ncw-config#80

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[Copilot]

Pull Request Overview

This PR enables AI functionality in the mail application and adds it to delegated settings. The changes include styling updates to exclude unified search modal elements from custom button styling and submodule updates to integrate the AI features.

• Updated button styling to preserve default appearance in unified search modal
• Updated mail submodule to integrate AI functionality
• Updated IONOS submodule for delegated settings support

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
apps/theming/css/ionos/buttons.css	Excludes unified search modal from custom button styling to prevent styling conflicts
apps-external/mail	Updates mail submodule to version with AI feature integration
IONOS	Updates IONOS submodule to support AI in delegated settings