feat(exam-homework): add audit report, i18n, error boundaries, and permission hardening

- Add comprehensive audit report for exam and homework module

- Create exam-homework i18n message files (zh-CN + en) and register namespace

- Add permission check to gradeHomeworkSubmissionAction to prevent horizontal privilege escalation

- Add Error Boundary + loading.tsx for 5 key pages (exam build/proctoring, homework assignment/submissions, student assignment)

- Refactor exam-columns to createExamColumns(t) factory for i18n support

- Refactor exam-data-table to manage columns internally via useTranslations

- Replace hardcoded strings with i18n keys in all exam/homework components and pages

- Add getHomeworkSubmissionForGrading data-access for secure grading flow

src/app/(dashboard)/teacher/homework/assignments/[id]/error.tsx

@@ -0,0 +1,24 @@
+"use client"
+
+import { AlertCircle } from "lucide-react"
+import { useTranslations } from "next-intl"
+
+import { EmptyState } from "@/shared/components/ui/empty-state"
+
+export default function AssignmentDetailError({ reset }: { error: Error & { digest?: string }; reset: () => void }) {
+  const t = useTranslations("examHomework")
+  return (
+    <div className="flex h-full flex-col items-center justify-center space-y-4 p-8">
+      <EmptyState
+        icon={AlertCircle}
+        title={t("homework.error.notFound")}
+        description={t("homework.error.assignmentNotFound")}
+        action={{
+          label: t("common.retry"),
+          onClick: () => reset(),
+        }}
+        className="border-none shadow-none h-auto"
+      />
+    </div>
+  )
+}

src/app/(dashboard)/teacher/homework/assignments/[id]/loading.tsx

@@ -0,0 +1,20 @@
+import { Skeleton } from "@/shared/components/ui/skeleton"
+
+export default function Loading() {
+  return (
+    <div className="flex h-full flex-col space-y-8 p-8">
+      <div className="space-y-2">
+        <Skeleton className="h-7 w-48" />
+        <Skeleton className="h-4 w-72" />
+      </div>
+      <div className="rounded-md border bg-card">
+        <div className="p-4 space-y-3">
+          <Skeleton className="h-8 w-full" />
+          <Skeleton className="h-16 w-full" />
+          <Skeleton className="h-16 w-full" />
+          <Skeleton className="h-16 w-full" />
+        </div>
+      </div>
+    </div>
+  )
+}

src/app/(dashboard)/teacher/homework/assignments/[id]/submissions/error.tsx

@@ -0,0 +1,24 @@
+"use client"
+
+import { AlertCircle } from "lucide-react"
+import { useTranslations } from "next-intl"
+
+import { EmptyState } from "@/shared/components/ui/empty-state"
+
+export default function SubmissionsError({ reset }: { error: Error & { digest?: string }; reset: () => void }) {
+  const t = useTranslations("examHomework")
+  return (
+    <div className="flex h-full flex-col items-center justify-center space-y-4 p-8">
+      <EmptyState
+        icon={AlertCircle}
+        title={t("homework.error.notFound")}
+        description={t("homework.error.submissionNotFound")}
+        action={{
+          label: t("common.retry"),
+          onClick: () => reset(),
+        }}
+        className="border-none shadow-none h-auto"
+      />
+    </div>
+  )
+}

src/app/(dashboard)/teacher/homework/assignments/[id]/submissions/loading.tsx

@@ -0,0 +1,20 @@
+import { Skeleton } from "@/shared/components/ui/skeleton"
+
+export default function Loading() {
+  return (
+    <div className="flex h-full flex-col space-y-8 p-8">
+      <div className="space-y-2">
+        <Skeleton className="h-7 w-40" />
+        <Skeleton className="h-4 w-72" />
+      </div>
+      <div className="rounded-md border bg-card">
+        <div className="p-4 space-y-3">
+          <Skeleton className="h-8 w-full" />
+          {Array.from({ length: 6 }).map((_, i) => (
+            <Skeleton key={i} className="h-12 w-full" />
+          ))}
+        </div>
+      </div>
+    </div>
+  )
+}

src/app/(dashboard)/teacher/homework/assignments/[id]/submissions/page.tsx

@@ -1,6 +1,7 @@
 import type { JSX } from "react"
 import Link from "next/link"
 import { notFound } from "next/navigation"
+import { getTranslations } from "next-intl/server"
 import { Badge } from "@/shared/components/ui/badge"
 import { Button } from "@/shared/components/ui/button"
 import {
@@ -18,6 +19,7 @@ export const dynamic = "force-dynamic"
 
 export default async function HomeworkAssignmentSubmissionsPage({ params }: { params: Promise<{ id: string }> }): Promise<JSX.Element> {
   const { id } = await params
+  const t = await getTranslations("examHomework")
   const [assignment, submissions] = await Promise.all([
     getHomeworkAssignmentById(id),
     getHomeworkSubmissions({ assignmentId: id }),
@@ -28,24 +30,24 @@ export default async function HomeworkAssignmentSubmissionsPage({ params }: { pa
     <div className="flex h-full flex-col space-y-8 p-8">
       <div className="flex flex-col justify-between gap-4 md:flex-row md:items-center">
         <div className="min-w-0">
-          <h1 className="text-2xl font-bold tracking-tight">Submissions</h1>
+          <h1 className="text-2xl font-bold tracking-tight">{t("homework.grade.submissions")}</h1>
           <p className="text-muted-foreground truncate">{assignment.title}</p>
           <div className="mt-2 flex flex-wrap items-center gap-2 text-sm text-muted-foreground">
-            <span>Exam: {assignment.sourceExamTitle}</span>
+            <span>{t("homework.grade.exam")}: {assignment.sourceExamTitle}</span>
             <span aria-hidden="true">•</span>
-            <span className="tabular-nums">Targets: {assignment.targetCount}</span>
+            <span className="tabular-nums">{t("homework.grade.targets")}: {assignment.targetCount}</span>
             <span aria-hidden="true">•</span>
-            <span className="tabular-nums">Submitted: {assignment.submittedCount}</span>
+            <span className="tabular-nums">{t("homework.grade.submittedCount")}: {assignment.submittedCount}</span>
             <span aria-hidden="true">•</span>
-            <span className="tabular-nums">Graded: {assignment.gradedCount}</span>
+            <span className="tabular-nums">{t("homework.grade.gradedCount")}: {assignment.gradedCount}</span>
           </div>
         </div>
         <div className="flex items-center gap-2">
           <Button asChild variant="outline">
-            <Link href="/teacher/homework/submissions">Back</Link>
+            <Link href="/teacher/homework/submissions">{t("homework.grade.back")}</Link>
           </Button>
           <Button asChild variant="outline">
-            <Link href={`/teacher/homework/assignments/${id}`}>Open Assignment</Link>
+            <Link href={`/teacher/homework/assignments/${id}`}>{t("homework.grade.openAssignment")}</Link>
           </Button>
         </div>
       </div>
@@ -54,11 +56,11 @@ export default async function HomeworkAssignmentSubmissionsPage({ params }: { pa
         <Table>
           <TableHeader>
             <TableRow>
-              <TableHead>Student</TableHead>
-              <TableHead>Status</TableHead>
-              <TableHead>Submitted</TableHead>
-              <TableHead>Score</TableHead>
-              <TableHead>Action</TableHead>
+              <TableHead>{t("homework.grade.student")}</TableHead>
+              <TableHead>{t("homework.grade.status")}</TableHead>
+              <TableHead>{t("homework.grade.submitted")}</TableHead>
+              <TableHead>{t("homework.grade.score")}</TableHead>
+              <TableHead>{t("homework.grade.action")}</TableHead>
             </TableRow>
           </TableHeader>
           <TableBody>
@@ -69,13 +71,13 @@ export default async function HomeworkAssignmentSubmissionsPage({ params }: { pa
                   <Badge variant="outline" className="capitalize">
                     {s.status}
                   </Badge>
-                  {s.isLate ? <span className="ml-2 text-xs text-destructive">Late</span> : null}
+                  {s.isLate ? <span className="ml-2 text-xs text-destructive">{t("homework.grade.late")}</span> : null}
                 </TableCell>
                 <TableCell className="text-muted-foreground tabular-nums">{s.submittedAt ? formatDate(s.submittedAt) : "-"}</TableCell>
                 <TableCell className="tabular-nums">{typeof s.score === "number" ? s.score : "-"}</TableCell>
                 <TableCell>
                   <Link href={`/teacher/homework/submissions/${s.id}`} className="text-sm underline-offset-4 hover:underline">
-                    Grade
+                    {t("homework.grade.title")}
                   </Link>
                 </TableCell>
               </TableRow>