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)/parent/dashboard/page.tsx

@@ -1,11 +1,32 @@
 import { requireAuth } from "@/shared/lib/auth-guard"
 import { getParentDashboardData } from "@/modules/parent/data-access"
 import { ParentDashboard } from "@/modules/parent/components/parent-dashboard"
+import { ParentNoChildrenPage } from "@/modules/parent/components/parent-children-data-page"
+import { Users } from "lucide-react"
 
 export const dynamic = "force-dynamic"
 
 export default async function ParentDashboardPage() {
   const ctx = await requireAuth()
+
+  // 非 admin 且 dataScope 非 children 类型时，显示空状态
+  if (
+    ctx.dataScope.type !== "all" &&
+    !(ctx.dataScope.type === "children" && ctx.dataScope.childrenIds.length > 0)
+  ) {
+    return (
+      <div className="p-6 md:p-8">
+        <ParentNoChildrenPage
+          title="Parent Dashboard"
+          description="Here's an overview of your children."
+          icon={Users}
+          emptyTitle="No children linked"
+          emptyDescription="Your account is not linked to any student accounts yet. Please contact the school administrator."
+        />
+      </div>
+    )
+  }
+
   const data = await getParentDashboardData(ctx.userId)
 
   return (