feat(app): quiz vocabulary as multiple choice

The session settings' new Vocabulary section quizzes words as multiple
choice: their meaning (the default), their reading, the expression for
the meaning, or the reading and the meaning in turn ("Mixed"). The
wrong answers come from the other words studied; none of the word's
own meanings counts as wrong, whatever its case. A word without what is
asked, or without two others to draw from, stays a word to flip. It is
asked the same way each time it comes, and rated as any card.

The settings keep both (`quizVocabulary`, `quizAspect`; settings schema
5), on every device.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/lib/l10n/app_localizations_en.dart

@@ -2033,6 +2033,32 @@ class AppLocalizationsEn extends AppLocalizations {
   String get studyModeCramHint =>
       'Walk every card without touching the schedules.';
 
+  @override
+  String get studySettingsVocabulary => 'Vocabulary';
+
+  @override
+  String get studySettingsQuizMc => 'Quiz with multiple choice';
+
+  @override
+  String get studySettingsQuizMcDescription =>
+      'Show vocabulary cards as a multiple-choice question, with wrong answers drawn from other vocabulary in this set.';
+
+  @override
+  String get studyAspectMeaning => 'Meaning';
+
+  @override
+  String get studyAspectReading => 'Reading';
+
+  @override
+  String get studyAspectExpression => 'Expression';
+
+  @override
+  String get studyAspectMixed => 'Mixed';
+
+  @override
+  String get studySettingsAspectDescription =>
+      'What to recall — the meaning, the kana reading, or the expression itself (shown the meaning). Mixed varies meaning and reading per card; cards that can’t be quizzed stay a normal flip.';
+
   @override
   String get studySortOldestFirst => 'Oldest first';