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/app/(dashboard)/teacher/exams/new/page.tsx

@@ -0,0 +1,18 @@
+import type { JSX } from "react"
+import { getTranslations } from "next-intl/server"
+import { ExamRichForm } from "@/modules/exams/components/exam-rich-form"
+
+export const dynamic = "force-dynamic"
+
+export default async function NewExamPage(): Promise<JSX.Element> {
+  const t = await getTranslations("examHomework")
+  return (
+    <div className="mx-auto w-full max-w-[1400px] space-y-6 p-6">
+      <div>
+        <h1 className="text-2xl font-bold tracking-tight">{t("exam.richEditor.title")}</h1>
+        <p className="text-muted-foreground">{t("exam.richEditor.description")}</p>
+      </div>
+      <ExamRichForm />
+    </div>
+  )
+}