feat(l10n): merge Crowdin updates, enable Korean at 98%

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).

lib/screens/settings/appearance_settings_page.dart

@@ -694,6 +694,7 @@ class _LanguageSelector extends StatelessWidget {
     ('es_ES', 'Español (España)', Icons.language),
     ('fr', 'Français', Icons.language),
     ('ja', '日本語', Icons.language),
+    ('ko', '한국어', Icons.language),
     ('pt', 'Português', Icons.language),
     ('pt_PT', 'Português (Brasil)', Icons.language),
     ('ru', 'Русский', Icons.language),

lib/screens/setup_screen.dart

@@ -710,6 +710,7 @@ class _SetupScreenState extends ConsumerState<SetupScreen> {
     ('es_ES', 'Español (España)', Icons.language),
     ('fr', 'Français', Icons.language),
     ('ja', '日本語', Icons.language),
+    ('ko', '한국어', Icons.language),
     ('pt', 'Português', Icons.language),
     ('pt_PT', 'Português (Brasil)', Icons.language),
     ('ru', 'Русский', Icons.language),