Focus participants during calls

[Comet1903]

Is your feature request related to a problem? Please describe.
In group calls, it is not possible to focus a specific participant’s video or profile. Users are limited to small thumbnails. The web version of Nextcloud Talk already supports this functionality, but it is missing in the iOS app.

Describe the solution you'd like
The ability to tap on a participant’s video or profile picture to expand it to full screen, similar to how it works in the web version.

Describe alternatives you've considered

• Using the web version for this functionality (less practical on mobile devices).

Additional context
No