Merge origin/l10n_main (PR #428) with a per-key three-way resolution:
Crowdin values win only where main did not change the key since the
last sync, so the unused-key removal, store->repo wording sweep, and
ICU plural fixes survive. Korean is restored at 98% completion and
mapped again in crowdin.yml and both language pickers; ar/hi/nl/zh-CN/
zh-TW stay dropped (37% and below).