fix: misc issues

[johanaam]

• Splits pupil and teacher classroom routes to remove route-name collisions.
• Removes classroom mock pupil data and stale placeholder/wrapper pages.
• Cleans up classroom details UI duplication and fixes edit/cancel labels.
• Adds missing locale keys and localizes remaining hard-coded pupil table text.
• Renames package metadata from frontend-temp to nettdetektivene-frontend.
• Fixes the Nyhetskvartalet intro i18n namespace.
• Adds/updates tests around routing, classroom API behavior, classroom details, and store replacement behavior.

[marikola]

looks good :)