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/modules/dashboard/components/teacher-dashboard/teacher-stats.tsx

@@ -1,8 +1,5 @@
-import Link from "next/link";
-import { Card, CardContent, CardHeader, CardTitle } from "@/shared/components/ui/card";
 import { FileCheck, PenTool, TrendingUp, BarChart } from "lucide-react";
-import { Skeleton } from "@/shared/components/ui/skeleton";
-import { cn } from "@/shared/lib/utils";
+import { StatCard } from "@/shared/components/ui/stat-card";
 
 interface TeacherStatsProps {
   toGradeCount: number;
@@ -19,84 +16,45 @@ export function TeacherStats({
   submissionRate,
   isLoading = false,
 }: TeacherStatsProps) {
-  if (isLoading) {
-    return (
-      <div className="grid gap-4 md:grid-cols-2 lg:grid-cols-4">
-        {Array.from({ length: 4 }).map((_, i) => (
-          <Card key={i}>
-            <CardHeader className="flex flex-row items-center justify-between space-y-0 pb-2">
-              <Skeleton className="h-4 w-[100px]" />
-              <Skeleton className="h-4 w-4 rounded-full" />
-            </CardHeader>
-            <CardContent>
-              <Skeleton className="h-8 w-[60px] mb-2" />
-              <Skeleton className="h-3 w-[140px]" />
-            </CardContent>
-          </Card>
-        ))}
-      </div>
-    );
-  }
-
-  const stats = [
-    {
-      title: "Needs Grading",
-      value: String(toGradeCount),
-      description: "Submissions pending review",
-      icon: FileCheck,
-      href: "/teacher/homework/submissions?status=submitted",
-      highlight: toGradeCount > 0,
-      color: "text-amber-500",
-    },
-    {
-      title: "Active Assignments",
-      value: String(activeAssignmentsCount),
-      description: "Published and ongoing",
-      icon: PenTool,
-      href: "/teacher/homework/assignments?status=published",
-      highlight: false,
-      color: "text-blue-500",
-    },
-    {
-      title: "Average Score",
-      value: `${Math.round(averageScore)}%`,
-      description: "Across recent assignments",
-      icon: TrendingUp,
-      href: "#grade-trends",
-      highlight: false,
-      color: "text-emerald-500",
-    },
-    {
-      title: "Submission Rate",
-      value: `${Math.round(submissionRate)}%`,
-      description: "Overall completion rate",
-      icon: BarChart,
-      href: "#grade-trends",
-      highlight: false,
-      color: "text-purple-500",
-    },
-  ] as const;
-
   return (
     <div className="grid gap-4 md:grid-cols-2 lg:grid-cols-4">
-      {stats.map((stat, i) => (
-        <Link key={i} href={stat.href} className="block transition-transform hover:-translate-y-1">
-          <Card className={cn(stat.highlight && "border-amber-200 bg-amber-50/50 dark:border-amber-900 dark:bg-amber-950/20")}>
-            <CardHeader className="flex flex-row items-center justify-between space-y-0 pb-2">
-              <CardTitle className="text-sm font-medium">
-                {stat.title}
-              </CardTitle>
-              <stat.icon className={cn("h-4 w-4", stat.color)} />
-            </CardHeader>
-            <CardContent>
-              <div className="text-2xl font-bold">{stat.value}</div>
-              <p className="text-xs text-muted-foreground">
-                {stat.description}
-              </p>
-            </CardContent>
-          </Card>
-        </Link>
-      ))}
+      <StatCard
+        title="Needs Grading"
+        value={String(toGradeCount)}
+        description="Submissions pending review"
+        icon={FileCheck}
+        href="/teacher/homework/submissions?status=submitted"
+        highlight={toGradeCount > 0}
+        color="text-amber-500"
+        isLoading={isLoading}
+      />
+      <StatCard
+        title="Active Assignments"
+        value={String(activeAssignmentsCount)}
+        description="Published and ongoing"
+        icon={PenTool}
+        href="/teacher/homework/assignments?status=published"
+        color="text-blue-500"
+        isLoading={isLoading}
+      />
+      <StatCard
+        title="Average Score"
+        value={`${Math.round(averageScore)}%`}
+        description="Across recent assignments"
+        icon={TrendingUp}
+        href="#grade-trends"
+        color="text-emerald-500"
+        isLoading={isLoading}
+      />
+      <StatCard
+        title="Submission Rate"
+        value={`${Math.round(submissionRate)}%`}
+        description="Overall completion rate"
+        icon={BarChart}
+        href="#grade-trends"
+        color="text-purple-500"
+        isLoading={isLoading}
+      />
     </div>
   );
 }