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/dashboard/page.tsx

@@ -3,27 +3,31 @@ import { getStudentClasses, getStudentSchedule } from "@/modules/classes/data-ac
 import { getStudentDashboardGrades, getStudentHomeworkAssignments } from "@/modules/homework/data-access"
 import { getCurrentStudentUser } from "@/modules/users/data-access"
 import { EmptyState } from "@/shared/components/ui/empty-state"
-import { Inbox } from "lucide-react"
+import { UserX } from "lucide-react"
+import type { StudentHomeworkProgressStatus } from "@/modules/homework/types"
 
 export const dynamic = "force-dynamic"
 
 const toWeekday = (d: Date): 1 | 2 | 3 | 4 | 5 | 6 | 7 => {
+  // getDay() 返回 0(周日)-6(周六)，转换为 1-7（周一为 1）
+  const WEEKDAY_MAP = [7, 1, 2, 3, 4, 5, 6] as const
   const day = d.getDay()
-  return (day === 0 ? 7 : day) as 1 | 2 | 3 | 4 | 5 | 6 | 7
+  if (day < 0 || day > 6) {
+    throw new Error(`Invalid day from getDay(): ${day}`)
+  }
+  return WEEKDAY_MAP[day]
 }
 
 export default async function StudentDashboardPage() {
   const student = await getCurrentStudentUser()
   if (!student) {
     return (
-      <div className="flex h-full flex-col items-center justify-center">
-        <EmptyState
-          title="No user found"
-          description="Create a student user to see dashboard."
-          icon={Inbox}
-          className="border-none shadow-none h-auto"
-        />
-      </div>
+      <EmptyState
+        title="No user found"
+        description="Create a student user to see dashboard."
+        icon={UserX}
+        className="border-none shadow-none h-auto"
+      />
     )
   }
 
@@ -38,19 +42,24 @@ export default async function StudentDashboardPage() {
   const in7Days = new Date(now)
   in7Days.setDate(in7Days.getDate() + 7)
 
-  const dueSoonCount = assignments.filter((a) => {
-    if (!a.dueAt) return false
+  // 单次遍历统计，避免重复 filter（PERF-04）
+  let dueSoonCount = 0
+  let overdueCount = 0
+  let gradedCount = 0
+  for (const a of assignments) {
+    const status: StudentHomeworkProgressStatus = a.progressStatus
+    if (status === "graded") {
+      gradedCount++
+      continue
+    }
+    if (!a.dueAt) continue
     const due = new Date(a.dueAt)
-    return due >= now && due <= in7Days && a.progressStatus !== "graded"
-  }).length
-
-  const overdueCount = assignments.filter((a) => {
-    if (!a.dueAt) return false
-    const due = new Date(a.dueAt)
-    return due < now && a.progressStatus !== "graded"
-  }).length
-
-  const gradedCount = assignments.filter((a) => a.progressStatus === "graded").length
+    if (due >= now && due <= in7Days) {
+      dueSoonCount++
+    } else if (due < now) {
+      overdueCount++
+    }
+  }
 
   const todayWeekday = toWeekday(now)
   const todayScheduleItems = schedule
@@ -75,15 +84,21 @@ export default async function StudentDashboardPage() {
     .slice(0, 6)
 
   return (
-    <StudentDashboard
-      studentName={student.name}
-      enrolledClassCount={classes.length}
-      dueSoonCount={dueSoonCount}
-      overdueCount={overdueCount}
-      gradedCount={gradedCount}
-      todayScheduleItems={todayScheduleItems}
-      upcomingAssignments={upcomingAssignments}
-      grades={grades}
-    />
+    <div className="space-y-8">
+      <div>
+        <h2 className="text-2xl font-bold tracking-tight">Dashboard</h2>
+        <p className="text-muted-foreground">Welcome back, {student.name}.</p>
+      </div>
+      <StudentDashboard
+        studentName={student.name}
+        enrolledClassCount={classes.length}
+        dueSoonCount={dueSoonCount}
+        overdueCount={overdueCount}
+        gradedCount={gradedCount}
+        todayScheduleItems={todayScheduleItems}
+        upcomingAssignments={upcomingAssignments}
+        grades={grades}
+      />
+    </div>
   )
 }