fix(M-AI-07-06): answer leak fixes (A3/A4) + state compatibility

- getQuizQuestions: only return answer/explanation after user has submitted
- findOne: remove questions include (use getQuizQuestions instead)
- State mapping: lifecycleStatus compatible with legacy status field

Co-Authored-By: Claude <noreply@anthropic.com>

src/modules/ai-runtime/user-ai.service.ts

@@ -546,11 +546,20 @@ export class UserAiService {
   async getQuizQuestions(userId: string, quizId: string) {
     const quiz = await this.prisma.quiz.findFirst({ where: { id: quizId, userId }, select: { id: true } });
     if (!quiz) throw new NotFoundException({ errorCode: 'QUIZ_NOT_FOUND', message: 'Quiz not found' });
+
+    // M-AI-07-06: 检查用户是否已提交过该 Quiz（至少一次 attempt finished）
+    const hasAttempt = await this.prisma.quizAttempt.findFirst({
+      where: { quizId, userId, finishedAt: { not: null } },
+      select: { id: true },
+    });
+
     return this.prisma.quizQuestion.findMany({
       where: { quizId },
       select: {
         id: true, type: true, stem: true, options: true,
-        answer: true, explanation: true, sourceBlockIds: true, orderIndex: true,
+        // ★ M-AI-07-06: 答案和解析仅在用户已提交后返回
+        ...(hasAttempt ? { answer: true, explanation: true } : {}),
+        sourceBlockIds: true, orderIndex: true,
       },
       orderBy: { orderIndex: 'asc' },
     });

src/modules/quiz/quiz.service.ts

@@ -82,7 +82,9 @@ export class QuizService {
 
   async findOne(id: string) {
     const quiz = await this.prisma.quiz.findUnique({
-      where: { id }, include: { questions: { orderBy: { orderIndex: 'asc' } } },
+      where: { id },
+      // M-AI-07-06: 不 include questions（避免答案泄漏）
+      // 客户端应使用 getQuizQuestions 获取题目，submit 后通过 getResults 获取答案
     });
     if (!quiz) throw new NotFoundException('测验不存在');
     return quiz;