feat(exams,homework): add rich text exam editor and scan-based grading

- Add Tiptap-based rich text editor with custom extensions (dotted-mark,
  blank-node, image-node, group-block, question-block) for exam creation
- Add AI auto-marking action to convert pasted exam text to structured editor doc
- Add resizable split-panel layout for editor + live preview
- Add student scan upload (photo of paper answers) with drag-drop and reorder
- Add scan image viewer with zoom/rotate/fullscreen for teachers
- Add scan grading view with side-by-side questions and scan images
- Add /teacher/exams/new and /teacher/homework/submissions/[id]/scan-grading routes
- Fix getScansAction to support both teacher (HOMEWORK_GRADE) and student
  (HOMEWORK_SUBMIT) permission scopes
- Add i18n keys for rich editor, scan upload, and scan grading (zh-CN/en)
- Sync architecture diagrams (004/005) with new modules, routes, and deps

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

@@ -21,12 +21,13 @@ import {
   AlertDialogHeader,
   AlertDialogTitle,
 } from "@/shared/components/ui/alert-dialog"
-import { Clock, CheckCircle2, Save, FileText, ChevronLeft, TriangleAlert, CloudUpload, CloudOff, Check, Loader2, Timer } from "lucide-react"
+import { Clock, CheckCircle2, Save, FileText, ChevronLeft, TriangleAlert, CloudUpload, CloudOff, Check, Loader2, Timer, Camera } from "lucide-react"
 import { formatDate, cn } from "@/shared/lib/utils"
 
 import type { StudentHomeworkTakeData } from "../types"
-import { saveHomeworkAnswerAction, startHomeworkSubmissionAction, submitHomeworkAction } from "../actions"
+import { saveHomeworkAnswerAction, startHomeworkSubmissionAction, submitHomeworkAction, getScansAction, deleteScanAction } from "../actions"
 import { QuestionRenderer } from "./question-renderer"
+import { ScanUploader, type ScanImage } from "./scan-uploader"
 import { parseSavedAnswer } from "../lib/question-content-utils"
 import { useDebouncedAutoSave, loadOfflineCache, clearOfflineCache } from "../hooks/use-debounced-auto-save"
 import { useExamCountdown } from "../hooks/use-exam-countdown"
@@ -43,6 +44,26 @@ export function HomeworkTakeView({ assignmentId, initialData }: HomeworkTakeView
   const [submissionStatus, setSubmissionStatus] = useState<string>(initialData.submission?.status ?? "not_started")
   const [isBusy, setIsBusy] = useState(false)
   const [showSubmitConfirm, setShowSubmitConfirm] = useState(false)
+  const [scanImages, setScanImages] = useState<ScanImage[]>([])
+
+  // 加载已有答题扫描图(拍照上传)
+  useEffect(() => {
+    if (!submissionId) return
+    void (async () => {
+      const result = await getScansAction(submissionId)
+      if (result.success && result.data) {
+        setScanImages(result.data)
+      }
+    })()
+  }, [submissionId])
+
+  const handleDeleteScan = async (fileId: string) => {
+    if (!submissionId) return
+    const result = await deleteScanAction(submissionId, fileId)
+    if (!result.success) {
+      toast.error(result.message || t("homework.take.saveFailed"))
+    }
+  }
 
   const initialAnswersByQuestionId = useMemo(() => {
     const map = new Map<string, { answer: unknown }>()
@@ -357,6 +378,29 @@ export function HomeworkTakeView({ assignmentId, initialData }: HomeworkTakeView
                 </Card>
               )
             })}
+
+            {showQuestions && submissionId && (
+              <Card className="border-l-4 border-l-blue-500 shadow-sm">
+                <CardHeader className="pb-2">
+                  <div className="flex items-center gap-2">
+                    <Camera className="h-4 w-4 text-blue-500" />
+                    <h3 className="font-semibold text-sm">{t("homework.take.scanTitle")}</h3>
+                  </div>
+                  <p className="text-xs text-muted-foreground mt-1">
+                    {t("homework.take.scanDescription")}
+                  </p>
+                  <div className="mt-3">
+                    <ScanUploader
+                      images={scanImages}
+                      onChange={setScanImages}
+                      onDeleteScan={handleDeleteScan}
+                      submissionId={submissionId}
+                      disabled={!canEdit}
+                    />
+                  </div>
+                </CardHeader>
+              </Card>
+            )}
           </div>
         </ScrollArea>
       </div>