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)/teacher/schedule-changes/page.tsx

@@ -1,3 +1,4 @@
+import type { JSX } from "react"
 import { ClipboardList } from "lucide-react"
 
 import { EmptyState } from "@/shared/components/ui/empty-state"
@@ -12,7 +13,7 @@ import { ScheduleChangeList } from "@/modules/scheduling/components/schedule-cha
 
 export const dynamic = "force-dynamic"
 
-export default async function TeacherScheduleChangesPage() {
+export default async function TeacherScheduleChangesPage(): Promise<JSX.Element> {
   const ctx = await getAuthContext()
 
   // Teachers see only their own requests; admins landing here see all.
@@ -34,7 +35,7 @@ export default async function TeacherScheduleChangesPage() {
   return (
     <div className="flex h-full flex-col space-y-8 p-8">
       <div className="space-y-1">
-        <h2 className="text-2xl font-bold tracking-tight">Schedule Change Requests</h2>
+        <h1 className="text-2xl font-bold tracking-tight">Schedule Change Requests</h1>
         <p className="text-muted-foreground">
           Submit a schedule change or substitute teacher request, and track its status.
         </p>
@@ -51,7 +52,7 @@ export default async function TeacherScheduleChangesPage() {
           <ScheduleChangeForm classes={classOptions} teachers={teacherOptions} />
 
           <div className="space-y-2">
-            <h3 className="text-lg font-semibold">My Requests</h3>
+            <h2 className="text-lg font-semibold">My Requests</h2>
             {items.length === 0 ? (
               <EmptyState
                 icon={ClipboardList}