Add theme toggle button for non-admin users

[wojcik91]

Description

Normal users don't see the navbar, because they can only access the profile page.

As a consequence they currently cannot switch between the light and dark theme.

[teon]

@Va1ter please propose approach

[Va1ter]

@teon Filip has already created same issue - here is the proposition. And the bottom part in the left (primary navigation) will be removed

CleanShot.2026-03-17.at.12.16.47.mp4

[filipslezaklab]

Duplicate of #2253