Replace the instructions translation domain with plain HTML files under
templates/backoffice/help/nl/. Each help/*.html.twig is now a locale
dispatch shim that tries the current locale first and falls back to nl,
so adding English (or any other language) is simply a matter of creating
a help/en/ directory with the translated files — no code changes needed.
Removes instructions+intl-icu.nl.xliff.
Add a 50/50 or 66/33 split layout to every backoffice page with Dutch
instructions explaining how to use Tijd voor de Test. Content covers the
overall workflow, quiz finalize/activate flow, and both candidate
participation methods (own device vs. shared laptop).
Help text lives in dedicated partials under templates/backoffice/help/ and
is loaded via Twig include(), keeping page templates clean. All strings use
a separate 'instructions' translation domain (instructions+intl-icu.nl.xliff)
isolated from the main messages domain.
Also updates 'Finalize'-related Dutch translations to use 'Afronden' and
adds tooltips to the finalize/unfinalize buttons.
Marijn
