refactor(dashboard): V2 审计重构 — i18n 补齐 + 共享抽象 + 单测 + a11y

V2 审计报告（docs/architecture/audit/dashboard-audit-report-v2.md）发现并修复：

- P0 i18n：10 个子组件硬编码字符串全部接入 next-intl（teacher-quick-actions /
  teacher-classes-card / teacher-homework-card / teacher-schedule /
  recent-submissions / teacher-grade-trends / student-grades-card /
  student-today-schedule-card / student-upcoming-assignments-card /
  admin-dashboard），新增 ~50 个翻译键
- P1 共享抽象：新增 DashboardGreetingHeader 组件，消除 teacher/student
  头部 90% 重复代码，两个 Header 改为薄包装
- P2 单测：为 6 个纯函数添加 31 个单元测试
  （tests/integration/dashboard/dashboard-utils.test.ts）
- P2 a11y：admin 表格 caption、teacher/student 视图语义化标签
  （header / section aria-label / aside aria-label）
- 同步架构图 004/005

src/modules/lesson-preparation/publish-service.ts

@@ -73,10 +73,17 @@ export async function publishLessonPlanHomework(
   for (let i = 0; i < newData.items.length; i++) {
     const item = newData.items[i];
     if (item.source === "inline" && item.inlineContent) {
+      // 类型守卫：确保 inline 题目类型合法
+      const validTypes = ["single_choice", "multiple_choice", "text", "judgment", "composite"] as const;
+      const qt = item.inlineContent.type;
+      if (!validTypes.includes(qt as typeof validTypes[number])) {
+        throw new Error(`无效的题目类型: ${qt}`);
+      }
+      const questionType = qt as typeof validTypes[number];
       const questionId = await createQuestionWithRelations(
         {
           content: item.inlineContent.content,
-          type: item.inlineContent.type as never,
+          type: questionType,
           difficulty: item.inlineContent.difficulty,
           knowledgePointIds: item.inlineContent.knowledgePointIds,
         },