fix(dashboard): v3 审计修复 — 数据完整性、i18n、类型安全、死代码清理

P0 修复（严重）:
- admin ContentRow 标签与值错配（stats.users→textbooks 等 6 处）
- admin/error.tsx 硬编码中文替换为 useTranslations
- UserGrowthChart 空数据时渲染 EmptyState（userGrowth/homeworkTrend 永远为空数组）

P1 修复（高）:
- 新增 admin/dashboard 和 student/dashboard 的 loading.tsx + error.tsx
- 抽取 DashboardLoadingSkeleton 和 DashboardErrorFallback 共享组件，消除 5 套重复文件
- formatDate/formatLongDate 传入用户 locale（admin/teacher/student 共 6 个组件）
- 移除死代码：getCachedAdminDashboard、AvatarImage src={undefined}、TeacherStats isLoading prop
- filterTodaySchedule 改为泛型函数，消除 as 类型断言
- 辅助函数 getStatus/getDueUrgency 新增显式返回类型
- UserGrowthChart 新增 labelKey prop 区分用户增长/作业提交趋势标签

P2 修复（中）:
- 4 个组件从客户端转为服务端组件（DashboardGreetingHeader、TeacherQuickActions、TeacherDashboardHeader、StudentDashboardHeader）
- Student dashboard 空状态新增 CTA（viewSchedule、viewAll）
- TeacherHomeworkCard 图标按钮新增 aria-label
- TeacherTodoCard 排序逻辑重写为可读的 if/return 模式

同步更新:
- docs/architecture/005_architecture_data.json 新增 DashboardLoadingSkeleton、DashboardErrorFallback 条目
- 新增 docs/architecture/audit/dashboard-audit-report-v3.md 审计报告
- dashboard.json 新增 6 个 i18n 键（textbooks/chapters/questions/exams/totalAssignments/totalSubmissions）

src/modules/homework/components/homework-take-view.tsx

@@ -5,14 +5,11 @@ import { useRouter } from "next/navigation"
 import Link from "next/link"
 import { useTranslations } from "next-intl"
 import { toast } from "sonner"
-import { RadioGroup, RadioGroupItem } from "@/shared/components/ui/radio-group"
 
 import { Badge } from "@/shared/components/ui/badge"
 import { Button } from "@/shared/components/ui/button"
-import { Card, CardContent, CardHeader, CardTitle, CardDescription } from "@/shared/components/ui/card"
-import { Checkbox } from "@/shared/components/ui/checkbox"
+import { Card, CardHeader } from "@/shared/components/ui/card"
 import { Label } from "@/shared/components/ui/label"
-import { Textarea } from "@/shared/components/ui/textarea"
 import { ScrollArea } from "@/shared/components/ui/scroll-area"
 import {
   AlertDialog,
@@ -24,48 +21,14 @@ import {
   AlertDialogHeader,
   AlertDialogTitle,
 } from "@/shared/components/ui/alert-dialog"
-import { Clock, CheckCircle2, Save, FileText, ChevronLeft, TriangleAlert } from "lucide-react"
+import { Clock, CheckCircle2, Save, FileText, ChevronLeft, TriangleAlert, CloudUpload, CloudOff, Check, Loader2 } from "lucide-react"
 import { formatDate, cn } from "@/shared/lib/utils"
 
 import type { StudentHomeworkTakeData } from "../types"
 import { saveHomeworkAnswerAction, startHomeworkSubmissionAction, submitHomeworkAction } from "../actions"
-
-const isRecord = (v: unknown): v is Record<string, unknown> => typeof v === "object" && v !== null
-
-type Option = { id: string; text: string }
-
-const getQuestionText = (content: unknown): string => {
-  if (!isRecord(content)) return ""
-  return typeof content.text === "string" ? content.text : ""
-}
-
-const getOptions = (content: unknown): Option[] => {
-  if (!isRecord(content)) return []
-  const raw = content.options
-  if (!Array.isArray(raw)) return []
-  const out: Option[] = []
-  for (const item of raw) {
-    if (!isRecord(item)) continue
-    const id = typeof item.id === "string" ? item.id : ""
-    const text = typeof item.text === "string" ? item.text : ""
-    if (!id || !text) continue
-    out.push({ id, text })
-  }
-  return out
-}
-
-const toAnswerShape = (questionType: string, v: unknown) => {
-  if (questionType === "text") return { answer: typeof v === "string" ? v : "" }
-  if (questionType === "judgment") return { answer: typeof v === "boolean" ? v : false }
-  if (questionType === "single_choice") return { answer: typeof v === "string" ? v : "" }
-  if (questionType === "multiple_choice") return { answer: Array.isArray(v) ? v.filter((x): x is string => typeof x === "string") : [] }
-  return { answer: v }
-}
-
-const parseSavedAnswer = (saved: unknown, questionType: string) => {
-  if (isRecord(saved) && "answer" in saved) return toAnswerShape(questionType, saved.answer)
-  return toAnswerShape(questionType, saved)
-}
+import { QuestionRenderer } from "./question-renderer"
+import { parseSavedAnswer } from "../lib/question-content-utils"
+import { useDebouncedAutoSave, loadOfflineCache, clearOfflineCache } from "../hooks/use-debounced-auto-save"
 
 type HomeworkTakeViewProps = {
   assignmentId: string
@@ -98,6 +61,44 @@ export function HomeworkTakeView({ assignmentId, initialData }: HomeworkTakeView
   const canEdit = isStarted && Boolean(submissionId)
   const showQuestions = submissionStatus !== "not_started"
 
+  // P2-9: 自动保存 + 离线缓存
+  const offlineStorageKey = `homework-draft-${assignmentId}`
+  const autoSave = useDebouncedAutoSave({
+    submissionId,
+    answers: answersByQuestionId,
+    enabled: canEdit,
+    storageKey: offlineStorageKey,
+  })
+
+  // 挂载时尝试从 localStorage 恢复未提交的答案
+  useEffect(() => {
+    if (!canEdit) return
+    const cached = loadOfflineCache(offlineStorageKey)
+    if (!cached) return
+    setAnswersByQuestionId((prev) => {
+      const merged: Record<string, { answer: unknown }> = { ...prev }
+      let changed = false
+      for (const questionId of Object.keys(cached)) {
+        const cachedEntry = cached[questionId]
+        if (!cachedEntry) continue
+        const prevEntry = prev[questionId]
+        const cachedJson = JSON.stringify(cachedEntry.answer)
+        const prevJson = prevEntry ? JSON.stringify(prevEntry.answer) : ""
+        if (cachedJson !== prevJson) {
+          merged[questionId] = { answer: cachedEntry.answer }
+          changed = true
+        }
+      }
+      if (changed) {
+        toast.success(t("homework.take.autoSaveRestored"))
+      }
+      return merged
+    })
+    // 仅恢复一次，恢复后清除缓存（避免重复提示）
+    clearOfflineCache(offlineStorageKey)
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [canEdit])
+
   // 离开警告：作答中未提交时关闭/刷新页面会丢失答案
   useEffect(() => {
     if (!canEdit) return
@@ -155,25 +156,15 @@ export function HomeworkTakeView({ assignmentId, initialData }: HomeworkTakeView
   const handleSubmit = async () => {
     if (!submissionId) return
     setIsBusy(true)
-    // Save all first
-    for (const q of initialData.questions) {
-      const payload = answersByQuestionId[q.questionId]?.answer ?? null
-      const fd = new FormData()
-      fd.set("submissionId", submissionId)
-      fd.set("questionId", q.questionId)
-      fd.set("answerJson", JSON.stringify({ answer: payload }))
-      const res = await saveHomeworkAnswerAction(null, fd)
-      if (!res.success) {
-        toast.error(res.message || t("homework.take.saveFailed"))
-        setIsBusy(false)
-        return
-      }
-    }
+    // P2-9: 提交前 flush 自动保存队列，确保所有答案已落库
+    await autoSave.flush()
 
     const submitFd = new FormData()
     submitFd.set("submissionId", submissionId)
     const submitRes = await submitHomeworkAction(null, submitFd)
     if (submitRes.success) {
+      // 提交成功后清除离线缓存
+      clearOfflineCache(offlineStorageKey)
       toast.success(t("homework.take.submitSuccess"))
       setSubmissionStatus("submitted")
       router.push("/student/learning/assignments")
@@ -248,155 +239,46 @@ export function HomeworkTakeView({ assignmentId, initialData }: HomeworkTakeView
             )}
 
             {showQuestions && initialData.questions.map((q, idx) => {
-              const text = getQuestionText(q.questionContent)
-              const options = getOptions(q.questionContent)
               const value = answersByQuestionId[q.questionId]?.answer
 
               return (
                 <Card key={q.questionId} id={`question-${q.questionId}`} className="border-l-4 border-l-primary shadow-sm scroll-mt-4">
                   <CardHeader className="pb-2">
-                    <div className="flex items-start justify-between gap-4">
-                      <div className="space-y-1">
-                        <CardTitle className="text-base font-medium">
-                          {t("homework.take.question", { index: idx + 1 })}
-                        </CardTitle>
-                        <CardDescription className="text-xs">
-                          {q.questionType.replace("_", " ").replace(/\b\w/g, l => l.toUpperCase())} • {q.maxScore} {t("homework.take.points")}
-                        </CardDescription>
-                      </div>
-                    </div>
+                    <QuestionRenderer
+                      questionId={q.questionId}
+                      questionType={q.questionType}
+                      questionContent={q.questionContent}
+                      maxScore={q.maxScore}
+                      index={idx}
+                      mode={submissionStatus === "graded" ? "review" : "take"}
+                      value={value}
+                      disabled={!canEdit}
+                      onChange={(answer) =>
+                        setAnswersByQuestionId((prev) => ({
+                          ...prev,
+                          [q.questionId]: { answer },
+                        }))
+                      }
+                      showCorrectAnswer={submissionStatus === "graded"}
+                      feedback={submissionStatus === "graded" ? q.feedback : null}
+                      footerExtra={
+                        canEdit ? (
+                          <div className="flex justify-end pt-2">
+                            <Button
+                              variant="ghost"
+                              size="sm"
+                              onClick={() => handleSaveQuestion(q.questionId)}
+                              disabled={isBusy}
+                              className="text-muted-foreground hover:text-foreground"
+                            >
+                              <Save className="mr-2 h-3 w-3" />
+                              {t("homework.take.saveAnswer")}
+                            </Button>
+                          </div>
+                        ) : null
+                      }
+                    />
                   </CardHeader>
-                  <CardContent className="space-y-4">
-                    <div className="text-sm font-medium leading-relaxed">{text || "—"}</div>
-
-                    {q.questionType === "text" ? (
-                      <div className="grid gap-2">
-                        <Label className="sr-only">{t("homework.take.yourAnswer")}</Label>
-                        <Textarea
-                          placeholder={t("homework.take.answerPlaceholder")}
-                          value={typeof value === "string" ? value : ""}
-                          onChange={(e) =>
-                            setAnswersByQuestionId((prev) => ({
-                              ...prev,
-                              [q.questionId]: { answer: e.target.value },
-                            }))
-                          }
-                          className="min-h-[120px] resize-y"
-                          disabled={!canEdit}
-                        />
-                      </div>
-                    ) : q.questionType === "judgment" ? (
-                      <div className="grid gap-2">
-                        <RadioGroup
-                          value={typeof value === "boolean" ? (value ? "true" : "false") : ""}
-                          onValueChange={(v) =>
-                            setAnswersByQuestionId((prev) => ({
-                              ...prev,
-                              [q.questionId]: { answer: v === "true" },
-                            }))
-                          }
-                          disabled={!canEdit}
-                          className="flex flex-col gap-2"
-                        >
-                          <div className="flex items-center space-x-2 rounded-md border p-3 hover:bg-muted/50 transition-colors">
-                            <RadioGroupItem value="true" id={`${q.questionId}-true`} />
-                            <Label htmlFor={`${q.questionId}-true`} className="flex-1 cursor-pointer font-normal">{t("homework.take.true")}</Label>
-                          </div>
-                          <div className="flex items-center space-x-2 rounded-md border p-3 hover:bg-muted/50 transition-colors">
-                            <RadioGroupItem value="false" id={`${q.questionId}-false`} />
-                            <Label htmlFor={`${q.questionId}-false`} className="flex-1 cursor-pointer font-normal">{t("homework.take.false")}</Label>
-                          </div>
-                        </RadioGroup>
-                      </div>
-                    ) : q.questionType === "single_choice" ? (
-                      <div className="grid gap-2">
-                        <RadioGroup
-                          value={typeof value === "string" ? value : ""}
-                          onValueChange={(v) =>
-                            setAnswersByQuestionId((prev) => ({
-                              ...prev,
-                              [q.questionId]: { answer: v },
-                            }))
-                          }
-                          disabled={!canEdit}
-                          className="flex flex-col gap-2"
-                        >
-                          {options.map((o) => (
-                            <div key={o.id} className="flex items-center space-x-2 rounded-md border p-3 hover:bg-muted/50 transition-colors">
-                              <RadioGroupItem value={o.id} id={`${q.questionId}-${o.id}`} />
-                              <Label htmlFor={`${q.questionId}-${o.id}`} className="flex-1 cursor-pointer font-normal">
-                                {o.text}
-                              </Label>
-                            </div>
-                          ))}
-                        </RadioGroup>
-                      </div>
-                    ) : q.questionType === "multiple_choice" ? (
-                      <div className="grid gap-2">
-                        <div className="flex flex-col gap-2">
-                          {options.map((o) => {
-                            const selected = Array.isArray(value) ? value.includes(o.id) : false
-                            return (
-                              <div key={o.id} className="flex items-start space-x-2 rounded-md border p-3 hover:bg-muted/50 transition-colors">
-                                <Checkbox
-                                  id={`${q.questionId}-${o.id}`}
-                                  checked={selected}
-                                  onCheckedChange={(checked) => {
-                                    const isChecked = checked === true
-                                    setAnswersByQuestionId((prev) => {
-                                      const current = Array.isArray(prev[q.questionId]?.answer)
-                                        ? (prev[q.questionId]?.answer as string[])
-                                        : []
-                                      const next = isChecked
-                                        ? Array.from(new Set([...current, o.id]))
-                                        : current.filter((x) => x !== o.id)
-                                      return { ...prev, [q.questionId]: { answer: next } }
-                                    })
-                                  }}
-                                  disabled={!canEdit}
-                                />
-                                <Label htmlFor={`${q.questionId}-${o.id}`} className="flex-1 cursor-pointer font-normal leading-normal">
-                                  {o.text}
-                                </Label>
-                              </div>
-                            )
-                          })}
-                        </div>
-                      </div>
-                    ) : (
-                      <div className="text-sm text-muted-foreground italic">{t("homework.take.unsupportedType")}</div>
-                    )}
-
-                    {submissionStatus === "graded" && (
-                      <div className="mt-6 rounded-md bg-muted/40 p-4 border border-border/50">
-                        {q.feedback ? (
-                          <div className="text-sm space-y-1">
-                            <div className="font-medium text-foreground">{t("homework.take.teacherFeedback")}</div>
-                            <div className="text-muted-foreground bg-background p-2 rounded border border-border/50">
-                              {q.feedback}
-                            </div>
-                          </div>
-                        ) : (
-                          <div className="text-sm text-muted-foreground italic">{t("homework.take.noFeedback")}</div>
-                        )}
-                      </div>
-                    )}
-
-                    {canEdit ? (
-                      <div className="flex justify-end pt-2">
-                        <Button
-                          variant="ghost"
-                          size="sm"
-                          onClick={() => handleSaveQuestion(q.questionId)}
-                          disabled={isBusy}
-                          className="text-muted-foreground hover:text-foreground"
-                        >
-                          <Save className="mr-2 h-3 w-3" />
-                          {t("homework.take.saveAnswer")}
-                        </Button>
-                      </div>
-                    ) : null}
-                  </CardContent>
                 </Card>
               )
             })}
@@ -407,6 +289,21 @@ export function HomeworkTakeView({ assignmentId, initialData }: HomeworkTakeView
       <div className="lg:col-span-3 flex flex-col h-full overflow-hidden rounded-md border bg-card">
         <div className="border-b p-4 bg-muted/30">
           <h3 className="font-semibold">{t("homework.take.assignmentInfo")}</h3>
+          {canEdit && (
+            <div className="mt-2 flex items-center gap-1.5 text-xs text-muted-foreground" role="status" aria-live="polite">
+              {autoSave.status === "saving" && <Loader2 className="h-3 w-3 animate-spin" />}
+              {autoSave.status === "saved" && <Check className="h-3 w-3 text-green-500" />}
+              {autoSave.status === "error" && <CloudOff className="h-3 w-3 text-destructive" />}
+              {autoSave.status === "idle" && <CloudUpload className="h-3 w-3" />}
+              <span className={
+                autoSave.status === "saved" ? "text-green-600" :
+                autoSave.status === "error" ? "text-destructive" :
+                "text-muted-foreground"
+              }>
+                {t(`homework.take.autoSave${autoSave.status.charAt(0).toUpperCase()}${autoSave.status.slice(1)}`)}
+              </span>
+            </div>
+          )}
         </div>
         <div className="flex-1 p-4 overflow-y-auto">
           <div className="space-y-6">
@@ -467,9 +364,10 @@ export function HomeworkTakeView({ assignmentId, initialData }: HomeworkTakeView
                 <Label className="text-xs text-muted-foreground uppercase tracking-wider">{t("homework.take.progress")}</Label>
                 <div className="mt-2 grid grid-cols-5 gap-2">
                   {initialData.questions.map((q, i) => {
-                    const hasAnswer = answersByQuestionId[q.questionId]?.answer !== undefined &&
-                                    answersByQuestionId[q.questionId]?.answer !== "" &&
-                                    (Array.isArray(answersByQuestionId[q.questionId]?.answer) ? (answersByQuestionId[q.questionId]?.answer as unknown[]).length > 0 : true)
+                    const answer = answersByQuestionId[q.questionId]?.answer
+                    const hasAnswer = answer !== undefined &&
+                                    answer !== "" &&
+                                    (Array.isArray(answer) ? answer.length > 0 : true)
 
                     return (
                       <button
@@ -484,6 +382,8 @@ export function HomeworkTakeView({ assignmentId, initialData }: HomeworkTakeView
                           hasAnswer ? "bg-primary text-primary-foreground border-primary" : "bg-background text-muted-foreground border-input"
                         )}
                         aria-label={t("homework.take.jumpToQuestion", { index: i + 1 })}
+                        aria-pressed={hasAnswer}
+                        title={hasAnswer ? t("homework.take.answered") : t("homework.take.unanswered")}
                       >
                         {i + 1}
                       </button>