- Add QuizQuestionType Swift enum with safe factory and displayAnswer
- Add QuizQuestion.questionType computed property
- Replace bare string comparisons with enum switch in QuizTakerView
- Add empty state, unknown type error state, judge localization
- Use displayAnswer in QuizResultView for choice index→text + judge CN
- Add QuizQuestionTypeTests (19 tests)
- Update QuizService with createAttempt/getAttemptQuestions endpoints
Co-Authored-By: Claude <noreply@anthropic.com>
