feat: 新增备课模块并修复全模块 P0/P1/P2 缺陷

主要变更:

- 新增 lesson-preparation 模块: 备课编辑器、节点编辑、AI 建议、知识点选择、版本历史、作业发布

- 新增 shared 通用组件: charts/question-bank-filters/schedule-list/ui (chip-nav/filter-bar/page-header/stat-card/stat-item)

- 新增 student/admin 端 loading.tsx 与 error.tsx, 优化加载与错误态体验

- 新增 teacher/lesson-plans 页面 (列表/新建/编辑)

- 新增 drizzle 迁移 0002_tiny_lionheart 及 snapshot

- 新增 textbooks/schema.ts 与 exams/utils/normalize-structure.ts

- 修复 Tiptap v3 SSR hydration 崩溃 (rich-text-block immediatelyRender: false)

- 重构多模块 data-access/actions/组件, 修复权限校验与类型规范

- 同步架构文档 004/005 反映新增模块、导出、依赖关系

- 归档 bugs/* 测试报告与 e2e 测试脚本 (admin/parent/student/teacher web_test)

src/app/(dashboard)/student/learning/textbooks/[id]/loading.tsx

@@ -0,0 +1,17 @@
+import { Skeleton } from "@/shared/components/ui/skeleton"
+
+export default function Loading() {
+  return (
+    <div className="flex h-[calc(100vh-4rem)] flex-col overflow-hidden">
+      <div className="flex items-center justify-between border-b py-3 px-6 shrink-0">
+        <div className="flex items-center gap-3">
+          <Skeleton className="h-6 w-48" />
+          <Skeleton className="h-5 w-16 rounded-full" />
+        </div>
+      </div>
+      <div className="flex-1 p-6">
+        <Skeleton className="h-full w-full" />
+      </div>
+    </div>
+  )
+}

src/app/(dashboard)/student/learning/textbooks/[id]/page.tsx

@@ -1,6 +1,6 @@
 import { notFound } from "next/navigation"
 
-import { BookOpen, Inbox } from "lucide-react"
+import { BookOpen } from "lucide-react"
 
 import { getTextbookById, getChaptersByTextbookId, getKnowledgePointsByTextbookId } from "@/modules/textbooks/data-access"
 import { TextbookReader } from "@/modules/textbooks/components/textbook-reader"
@@ -16,19 +16,7 @@ export default async function StudentTextbookDetailPage({
   params: Promise<{ id: string }>
 }) {
   const student = await getCurrentStudentUser()
-  if (!student) {
-    return (
-      <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
-        <div className="flex items-center justify-between space-y-2">
-          <div>
-            <h2 className="text-2xl font-bold tracking-tight">Textbook</h2>
-            <p className="text-muted-foreground">Read chapters and review content.</p>
-          </div>
-        </div>
-        <EmptyState title="No user found" description="Create a student user to read textbooks." icon={Inbox} />
-      </div>
-    )
-  }
+  if (!student) return notFound()
 
   const { id } = await params
 
@@ -46,7 +34,7 @@ export default async function StudentTextbookDetailPage({
         <div className="flex items-center gap-3 min-w-0">
           <h1 className="text-lg font-bold tracking-tight truncate">{textbook.title}</h1>
           <div className="flex items-center gap-2 text-sm text-muted-foreground">
-             <span className="hidden sm:inline-block w-px h-4 bg-border" />
+             <span className="hidden sm:inline-block w-px h-4 bg-border" aria-hidden="true" />
              <Badge variant="outline" className="font-normal text-xs">{textbook.subject}</Badge>
              {textbook.grade && (
                <Badge variant="secondary" className="font-normal text-xs">{textbook.grade}</Badge>