feat(dashboard): 仪表盘模块审计重构 — 权限校验 + i18n + 逻辑抽离

基于 dashboard-audit-report.md 审计结论，对仪表盘模块进行 P0/P1 级修复：

- 新增 4 个 dashboard 权限点（DASHBOARD_ADMIN/TEACHER/STUDENT/PARENT_READ），补充到 permissions.ts 和角色-权限映射

- 新建 actions.ts：4 个 Server Action 均调用 requirePermission() 校验权限，消除 admin 页面零鉴权、teacher/student/parent 仅 requireAuth 的安全隐患

- 根重定向页 /dashboard 改用 resolvePermissions() + 权限点判断，不再 role === xxx 硬编码

- 新建 lib/dashboard-utils.ts：抽取 toWeekday / countStudentAssignments / sortUpcomingAssignments / filterTodaySchedule / computeTeacherMetrics / getGreetingKey 纯函数，与 UI 分离，便于单测

- 新建 messages/{zh-CN,en}/dashboard.json 翻译文件，i18n request.ts 加载 dashboard 命名空间；所有视图组件接入 useTranslations / getTranslations，消除中英混杂硬编码

- 重构 4 个角色 page.tsx：通过 actions 获取数据，generateMetadata 使用 i18n

- 同步更新架构图 004 / 005 文档（dashboard exports / permissions / 文件清单）

src/modules/dashboard/components/teacher-dashboard/teacher-dashboard-view.tsx

@@ -1,4 +1,7 @@
-import type { TeacherDashboardData, TeacherTodayScheduleItem } from "@/modules/dashboard/types"
+import type { TeacherDashboardData } from "@/modules/dashboard/types"
+import type { TeacherDashboardMetrics } from "@/modules/dashboard/lib/dashboard-utils"
+import { getTranslations } from "next-intl/server"
+import type { TeacherTodoItem } from "./teacher-todo-card"
 
 import { TeacherClassesCard } from "./teacher-classes-card"
 import { TeacherDashboardHeader } from "./teacher-dashboard-header"
@@ -7,52 +10,36 @@ import { RecentSubmissions } from "./recent-submissions"
 import { TeacherSchedule } from "./teacher-schedule"
 import { TeacherStats } from "./teacher-stats"
 import { TeacherGradeTrends } from "./teacher-grade-trends"
-import { TeacherTodoCard, type TeacherTodoItem } from "./teacher-todo-card"
+import { TeacherTodoCard } from "./teacher-todo-card"
 
-const toWeekday = (d: Date): 1 | 2 | 3 | 4 | 5 | 6 | 7 => {
-  const day = d.getDay()
-  return (day === 0 ? 7 : day) as 1 | 2 | 3 | 4 | 5 | 6 | 7
+interface TeacherDashboardViewProps {
+  data: TeacherDashboardData & { metrics: TeacherDashboardMetrics }
 }
 
-export function TeacherDashboardView({ data }: { data: TeacherDashboardData }) {
-  const todayWeekday = toWeekday(new Date())
+export async function TeacherDashboardView({ data }: TeacherDashboardViewProps) {
+  const t = await getTranslations("dashboard")
+  const { metrics } = data
 
-  const classNameById = new Map(data.classes.map((c) => [c.id, c.name] as const))
-  const todayScheduleItems: TeacherTodayScheduleItem[] = data.schedule
-    .filter((s) => s.weekday === todayWeekday)
-    .sort((a, b) => a.startTime.localeCompare(b.startTime))
-    .map((s): TeacherTodayScheduleItem => ({
-      id: s.id,
-      classId: s.classId,
-      className: classNameById.get(s.classId) ?? "Class",
-      course: s.course,
-      startTime: s.startTime,
-      endTime: s.endTime,
-      location: s.location ?? null,
-    }))
-
-  const submittedSubmissions = data.submissions.filter((s) => Boolean(s.submittedAt))
-  const toGradeCount = submittedSubmissions.filter((s) => s.status === "submitted").length
-
-  const submissionsToGrade = submittedSubmissions
-    .filter(s => s.status === "submitted")
-    .sort((a, b) => (a.submittedAt ? new Date(a.submittedAt).getTime() : 0) - (b.submittedAt ? new Date(b.submittedAt).getTime() : 0))
-    .slice(0, 6);
-
-  const activeAssignmentsCount = data.assignments.filter(a => a.status === "published").length
-  
-  const totalTrendScore = data.gradeTrends.reduce((acc, curr) => acc + curr.averageScore, 0)
-  const averageScore = data.gradeTrends.length > 0 ? totalTrendScore / data.gradeTrends.length : 0
-
-  const totalSubmissions = data.gradeTrends.reduce((acc, curr) => acc + curr.submissionCount, 0)
-  const totalPotentialSubmissions = data.gradeTrends.reduce((acc, curr) => acc + curr.totalStudents, 0)
-  const submissionRate = totalPotentialSubmissions > 0 ? (totalSubmissions / totalPotentialSubmissions) * 100 : 0
-
-  // 待办聚合
+  // 待办聚合（使用预计算指标）
   const todoItems: TeacherTodoItem[] = [
-    { label: "待批改作业", count: toGradeCount, href: "/teacher/homework/submissions", variant: toGradeCount > 0 ? "urgent" : "normal" },
-    { label: "今日待考勤", count: todayScheduleItems.length, href: "/teacher/attendance/sheet", variant: "info" },
-    { label: "进行中作业", count: activeAssignmentsCount, href: "/teacher/homework/assignments", variant: "normal" },
+    {
+      label: t("todo.toGrade"),
+      count: metrics.toGradeCount,
+      href: "/teacher/homework/submissions",
+      variant: metrics.toGradeCount > 0 ? "urgent" : "normal",
+    },
+    {
+      label: t("todo.todayAttendance"),
+      count: metrics.todayScheduleItems.length,
+      href: "/teacher/attendance/sheet",
+      variant: "info",
+    },
+    {
+      label: t("todo.activeAssignments"),
+      count: metrics.activeAssignmentsCount,
+      href: "/teacher/homework/assignments",
+      variant: "normal",
+    },
   ]
 
   return (
@@ -60,34 +47,34 @@ export function TeacherDashboardView({ data }: { data: TeacherDashboardData }) {
       <TeacherDashboardHeader teacherName={data.teacherName} />
 
       <TeacherStats
-        toGradeCount={toGradeCount}
-        activeAssignmentsCount={activeAssignmentsCount}
-        averageScore={averageScore}
-        submissionRate={submissionRate}
+        toGradeCount={metrics.toGradeCount}
+        activeAssignmentsCount={metrics.activeAssignmentsCount}
+        averageScore={metrics.averageScore}
+        submissionRate={metrics.submissionRate}
       />
 
       <div className="grid gap-6 lg:grid-cols-12">
         {/* 移动端优先展示：今日课表 → 待办 → 待批改 */}
         <div className="flex flex-col gap-6 lg:col-span-8">
-            <div className="lg:hidden">
-              <TeacherSchedule items={todayScheduleItems} />
-            </div>
-            <TeacherTodoCard items={todoItems} />
-            <TeacherGradeTrends trends={data.gradeTrends} />
-            <RecentSubmissions 
-                submissions={submissionsToGrade} 
-                title="待批改"
-                emptyTitle="全部批改完成！"
-                emptyDescription="暂无待批改的提交。"
-            />
+          <div className="lg:hidden">
+            <TeacherSchedule items={metrics.todayScheduleItems} />
+          </div>
+          <TeacherTodoCard items={todoItems} />
+          <TeacherGradeTrends trends={data.gradeTrends} />
+          <RecentSubmissions
+            submissions={metrics.submissionsToGrade}
+            title={t("sections.pendingGrading")}
+            emptyTitle={t("empty.allGraded")}
+            emptyDescription={t("empty.allGradedDesc")}
+          />
         </div>
-        
+
         <div className="flex flex-col gap-6 lg:col-span-4">
-            <div className="hidden lg:block">
-              <TeacherSchedule items={todayScheduleItems} />
-            </div>
-            <TeacherHomeworkCard assignments={data.assignments} />
-            <TeacherClassesCard classes={data.classes} />
+          <div className="hidden lg:block">
+            <TeacherSchedule items={metrics.todayScheduleItems} />
+          </div>
+          <TeacherHomeworkCard assignments={data.assignments} />
+          <TeacherClassesCard classes={data.classes} />
         </div>
       </div>
     </div>