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/dashboard/components/student-dashboard/student-dashboard-header.tsx

@@ -1,26 +1,13 @@
 "use client"
 
-import { useTranslations } from "next-intl"
-import { formatLongDate } from "@/shared/lib/utils"
-import { getGreetingKey } from "@/modules/dashboard/lib/dashboard-utils"
+import { DashboardGreetingHeader } from "../dashboard-greeting-header"
 
 interface StudentDashboardHeaderProps {
   studentName: string
 }
 
 export function StudentDashboardHeader({ studentName }: StudentDashboardHeaderProps) {
-  const t = useTranslations("dashboard")
-  const today = formatLongDate(new Date())
-  const greetingKey = getGreetingKey(new Date())
-
   return (
-    <div className="flex flex-col justify-between space-y-4 md:flex-row md:items-center md:space-y-0">
-      <div>
-        <h2 className="text-2xl font-bold tracking-tight">
-          {t(`greeting.${greetingKey}`)}，{studentName}
-        </h2>
-        <p className="text-muted-foreground">{t("greeting.todayIs", { date: today })}</p>
-      </div>
-    </div>
+    <DashboardGreetingHeader userName={studentName} />
   )
 }

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

@@ -1,3 +1,5 @@
+import { getTranslations } from "next-intl/server"
+
 import type { StudentDashboardProps } from "@/modules/dashboard/types"
 
 import { DashboardSection } from "../dashboard-section"
@@ -17,9 +19,12 @@ export async function StudentDashboard({
   upcomingAssignments,
   grades,
 }: StudentDashboardProps) {
+  const t = await getTranslations("dashboard")
   return (
     <div className="space-y-6">
-      <StudentDashboardHeader studentName={studentName} />
+      <header>
+        <StudentDashboardHeader studentName={studentName} />
+      </header>
 
       <DashboardSection variant="stats">
         <StudentStatsGrid
@@ -32,19 +37,22 @@ export async function StudentDashboard({
       </DashboardSection>
 
       <div className="grid grid-cols-1 lg:grid-cols-3 gap-6">
-        <div className="lg:col-span-2 space-y-6">
+        <section
+          aria-label={t("sections.upcomingAssignments")}
+          className="lg:col-span-2 space-y-6"
+        >
           <DashboardSection variant="list">
             <StudentUpcomingAssignmentsCard upcomingAssignments={upcomingAssignments} />
           </DashboardSection>
           <DashboardSection variant="card">
             <StudentGradesCard grades={grades} />
           </DashboardSection>
-        </div>
-        <div className="space-y-6">
+        </section>
+        <aside aria-label={t("sections.todaySchedule")} className="space-y-6">
           <DashboardSection variant="card">
             <StudentTodayScheduleCard items={todayScheduleItems} />
           </DashboardSection>
-        </div>
+        </aside>
       </div>
     </div>
   )

src/modules/dashboard/components/student-dashboard/student-grades-card.tsx

@@ -2,7 +2,9 @@
 
 import Link from "next/link"
 import { BarChart3 } from "lucide-react"
+import { useTranslations } from "next-intl"
 
+import { Button } from "@/shared/components/ui/button"
 import { ChartCardShell } from "@/shared/components/charts/chart-card-shell"
 import { TrendLineChart } from "@/shared/components/charts/trend-line-chart"
 import { Table, TableBody, TableCell, TableHead, TableHeader, TableRow } from "@/shared/components/ui/table"
@@ -10,6 +12,7 @@ import { formatDate } from "@/shared/lib/utils"
 import type { StudentDashboardGradeProps } from "@/modules/homework/types"
 
 export function StudentGradesCard({ grades }: { grades: StudentDashboardGradeProps }) {
+  const t = useTranslations("dashboard")
   const hasGradeTrend = grades.trend.length > 0
   const hasRecentGrades = grades.recent.length > 0
 
@@ -26,13 +29,20 @@ export function StudentGradesCard({ grades }: { grades: StudentDashboardGradePro
 
   return (
     <ChartCardShell
-      title="Recent Grades"
+      title={t("sections.recentGrades")}
       icon={BarChart3}
       iconClassName="text-muted-foreground"
       isEmpty={!hasGradeTrend}
-      emptyTitle="No graded work yet"
-      emptyDescription="Finish and submit assignments to see your score trend."
+      emptyTitle={t("empty.noGradedWork")}
+      emptyDescription={t("empty.noGradedWorkDesc")}
       emptyClassName="h-72"
+      action={
+        hasGradeTrend ? (
+          <Button asChild variant="outline" size="sm">
+            <Link href="/student/grades">{t("quickActions.viewAll")}</Link>
+          </Button>
+        ) : null
+      }
     >
       <div className="space-y-4">
         <div className="rounded-md border bg-card p-4">
@@ -41,7 +51,7 @@ export function StudentGradesCard({ grades }: { grades: StudentDashboardGradePro
             series={[
               {
                 dataKey: "score",
-                name: "Score (%)",
+                name: t("chart.scorePercent"),
                 color: "hsl(var(--primary))",
                 dotRadius: 4,
                 activeDotRadius: 6,
@@ -56,13 +66,13 @@ export function StudentGradesCard({ grades }: { grades: StudentDashboardGradePro
           {latestGrade ? (
             <div className="mt-3 flex items-center justify-between text-sm text-muted-foreground">
               <div>
-                Latest:{" "}
+                {t("chart.latest")}:{" "}
                 <span className="font-medium text-foreground tabular-nums">
                   {Math.round(latestGrade.percentage)}%
                 </span>
               </div>
               <div>
-                Points:{" "}
+                {t("chart.points")}:{" "}
                 <span className="font-medium text-foreground tabular-nums">
                   {latestGrade.score}/{latestGrade.maxScore}
                 </span>
@@ -76,9 +86,9 @@ export function StudentGradesCard({ grades }: { grades: StudentDashboardGradePro
             <Table>
               <TableHeader>
                 <TableRow className="bg-muted/50">
-                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">Assignment</TableHead>
-                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">Score</TableHead>
-                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">When</TableHead>
+                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">{t("table.assignment")}</TableHead>
+                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">{t("table.score")}</TableHead>
+                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">{t("table.when")}</TableHead>
                 </TableRow>
               </TableHeader>
               <TableBody>

src/modules/dashboard/components/student-dashboard/student-today-schedule-card.tsx

@@ -3,6 +3,7 @@
 import { useMemo } from "react"
 import Link from "next/link"
 import { CalendarDays, CalendarX } from "lucide-react"
+import { useTranslations } from "next-intl"
 
 import { Button } from "@/shared/components/ui/button"
 import { Badge } from "@/shared/components/ui/badge"
@@ -12,18 +13,15 @@ import { EmptyState } from "@/shared/components/ui/empty-state"
 import { cn } from "@/shared/lib/utils"
 import type { StudentTodayScheduleItem } from "@/modules/dashboard/types"
 
-/**
- * Parse "HH:MM" time string into minutes since midnight for comparison.
- */
 const timeToMinutes = (t: string): number => {
   const [h, m] = t.split(":").map(Number)
   return (h ?? 0) * 60 + (m ?? 0)
 }
 
 export function StudentTodayScheduleCard({ items }: { items: StudentTodayScheduleItem[] }) {
+  const t = useTranslations("dashboard")
   const hasSchedule = items.length > 0
 
-  // Compute current/next class status based on client time
   const { currentId, nextId } = useMemo(() => {
     const now = new Date()
     const nowMin = now.getHours() * 60 + now.getMinutes()
@@ -49,18 +47,18 @@ export function StudentTodayScheduleCard({ items }: { items: StudentTodaySchedul
       <CardHeader className="flex flex-row items-center justify-between">
         <CardTitle className="flex items-center gap-2">
           <CalendarDays className="h-4 w-4 text-muted-foreground" />
-          Today&apos;s Schedule
+          {t("sections.todaySchedule")}
         </CardTitle>
         <Button asChild variant="outline" size="sm">
-          <Link href="/student/schedule">View all</Link>
+          <Link href="/student/schedule">{t("quickActions.viewAll")}</Link>
         </Button>
       </CardHeader>
       <CardContent>
         {!hasSchedule ? (
           <EmptyState
             icon={CalendarX}
-            title="No classes today"
-            description="Your timetable is clear for today."
+            title={t("empty.noClassesToday")}
+            description={t("empty.noClassesTodayDesc")}
             className="border-none h-72"
           />
         ) : (
@@ -74,14 +72,14 @@ export function StudentTodayScheduleCard({ items }: { items: StudentTodaySchedul
               if (isCurrent) {
                 return (
                   <Badge className="shrink-0 bg-emerald-500 text-white hover:bg-emerald-500">
-                    In Progress
+                    {t("badge.inProgress")}
                   </Badge>
                 )
               }
               if (isNext) {
                 return (
                   <Badge variant="outline" className="shrink-0 border-primary text-primary">
-                    Up Next
+                    {t("badge.upNext")}
                   </Badge>
                 )
               }

src/modules/dashboard/components/student-dashboard/student-upcoming-assignments-card.tsx

@@ -1,5 +1,6 @@
 import Link from "next/link"
 import { PenTool } from "lucide-react"
+import { getTranslations } from "next-intl/server"
 
 import { Badge } from "@/shared/components/ui/badge"
 import { Button } from "@/shared/components/ui/button"
@@ -14,11 +15,11 @@ import {
   STUDENT_HOMEWORK_PROGRESS_LABEL,
 } from "@/modules/homework/types"
 
-const getActionLabel = (status: string) => {
-  if (status === "graded") return "Review"
-  if (status === "submitted") return "View"
-  if (status === "in_progress") return "Continue"
-  return "Start"
+const getActionLabelKey = (status: string): "action.review" | "action.view" | "action.continue" | "action.start" => {
+  if (status === "graded") return "action.review"
+  if (status === "submitted") return "action.view"
+  if (status === "in_progress") return "action.continue"
+  return "action.start"
 }
 
 const getActionVariant = (status: string): "default" | "secondary" | "outline" => {
@@ -33,12 +34,13 @@ const getDueUrgency = (dueAt: string | null) => {
   const diffHours = (due.getTime() - now.getTime()) / (1000 * 60 * 60)
 
   if (diffHours < 0) return "overdue"
-  if (diffHours < 48) return "urgent" // 2 days
-  if (diffHours < 120) return "warning" // 5 days
+  if (diffHours < 48) return "urgent"
+  if (diffHours < 120) return "warning"
   return "normal"
 }
 
-export function StudentUpcomingAssignmentsCard({ upcomingAssignments }: { upcomingAssignments: StudentHomeworkAssignmentListItem[] }) {
+export async function StudentUpcomingAssignmentsCard({ upcomingAssignments }: { upcomingAssignments: StudentHomeworkAssignmentListItem[] }) {
+  const t = await getTranslations("dashboard")
   const hasAssignments = upcomingAssignments.length > 0
 
   return (
@@ -46,18 +48,18 @@ export function StudentUpcomingAssignmentsCard({ upcomingAssignments }: { upcomi
       <CardHeader className="flex flex-row items-center justify-between">
         <CardTitle className="text-base flex items-center gap-2">
           <PenTool className="h-4 w-4 text-muted-foreground" />
-          Upcoming Assignments
+          {t("sections.upcomingAssignments")}
         </CardTitle>
         <Button asChild variant="outline" size="sm">
-          <Link href="/student/learning/assignments">View all</Link>
+          <Link href="/student/learning/assignments">{t("quickActions.viewAll")}</Link>
         </Button>
       </CardHeader>
       <CardContent>
         {!hasAssignments ? (
           <EmptyState
             icon={PenTool}
-            title="No assignments"
-            description="You have no assigned homework right now."
+            title={t("empty.noAssignmentsStudent")}
+            description={t("empty.noAssignmentsStudentDesc")}
             className="border-none h-72"
           />
         ) : (
@@ -65,18 +67,18 @@ export function StudentUpcomingAssignmentsCard({ upcomingAssignments }: { upcomi
             <Table>
               <TableHeader>
                 <TableRow className="bg-muted/50">
-                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">Title</TableHead>
-                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">Status</TableHead>
-                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">Due</TableHead>
-                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">Score</TableHead>
-                  <TableHead className="text-xs font-medium uppercase text-muted-foreground text-right">Action</TableHead>
+                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">{t("table.title")}</TableHead>
+                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">{t("table.status")}</TableHead>
+                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">{t("table.due")}</TableHead>
+                  <TableHead className="text-xs font-medium uppercase text-muted-foreground">{t("table.score")}</TableHead>
+                  <TableHead className="text-xs font-medium uppercase text-muted-foreground text-right">{t("table.action")}</TableHead>
                 </TableRow>
               </TableHeader>
               <TableBody>
                 {upcomingAssignments.map((a) => {
                   const urgency = getDueUrgency(a.dueAt)
                   const isGraded = a.progressStatus === "graded"
-                  
+
                   return (
                     <TableRow key={a.id} className="h-12">
                       <TableCell className="font-medium">
@@ -85,7 +87,7 @@ export function StudentUpcomingAssignmentsCard({ upcomingAssignments }: { upcomi
                             {a.title}
                           </Link>
                           {!isGraded && urgency === "overdue" && (
-                             <Badge variant="destructive" className="h-5 px-1.5 text-[10px] uppercase">Late</Badge>
+                             <Badge variant="destructive" className="h-5 px-1.5 text-[10px] uppercase">{t("badge.late")}</Badge>
                           )}
                         </div>
                       </TableCell>
@@ -107,7 +109,7 @@ export function StudentUpcomingAssignmentsCard({ upcomingAssignments }: { upcomi
                       <TableCell className="text-right">
                         <Button asChild size="sm" variant={getActionVariant(a.progressStatus)} className="h-7 text-xs">
                           <Link href={`/student/learning/assignments/${a.id}`}>
-                            {getActionLabel(a.progressStatus)}
+                            {t(getActionLabelKey(a.progressStatus))}
                           </Link>
                         </Button>
                       </TableCell>