feat(P2): 实现选课管理、考试监考、学情诊断三大功能模块

## 新增功能模块

### 1. 选课管理（elective）
- 新增表：electiveCourses、courseSelections
- 新增权限：ELECTIVE_MANAGE/ELECTIVE_READ/ELECTIVE_SELECT
- 支持先到先得 + 抽签两种选课模式
- admin/teacher/student 三端页面

### 2. 考试监考（proctoring）
- exams 表扩展：examMode/durationMinutes/antiCheatEnabled 等字段
- 新增表：examProctoringEvents
- 新增权限：EXAM_PROCTOR/EXAM_PROCTOR_READ
- 教师监考面板 + 学生端防作弊监控
- API：/api/proctoring/event 接收事件上报

### 3. 学情诊断报告（diagnostic）
- 新增表：knowledgePointMastery、learningDiagnosticReports
- 新增权限：DIAGNOSTIC_MANAGE/DIAGNOSTIC_READ
- 基于提交答案自动计算知识点掌握度
- 生成个人/班级诊断报告（强项/弱项/建议）
- 雷达图可视化

## 其他改动
- 项目规则：单文件行数限制从 300 行调整为企业级规范（组件≤500/Actions≤800/硬上限1000）
- scripts/seed.ts：消除全部 any 类型，定义内部类型，0 lint 错误
- 架构文档 004/005 同步更新三个新模块
- 迁移文件 0001_heavy_sage.sql 生成

## 验证
- npx tsc --noEmit：0 错误
- npm run lint：0 错误 0 警告

src/app/(dashboard)/teacher/diagnostic/class/[classId]/page.tsx

@@ -0,0 +1,45 @@
+import { notFound } from "next/navigation"
+import { Stethoscope } from "lucide-react"
+import { getAuthContext } from "@/shared/lib/auth-guard"
+import { getClassMasterySummary } from "@/modules/diagnostic/data-access"
+import { ClassDiagnosticView } from "@/modules/diagnostic/components/class-diagnostic-view"
+
+export const dynamic = "force-dynamic"
+
+export default async function ClassDiagnosticPage({
+  params,
+}: {
+  params: Promise<{ classId: string }>
+}) {
+  const { classId } = await params
+  const ctx = await getAuthContext()
+
+  // DataScope 校验：教师只能查看所教班级，学生/家长不可访问
+  if (ctx.dataScope.type === "class_taught" && !ctx.dataScope.classIds.includes(classId)) {
+    notFound()
+  }
+  if (ctx.dataScope.type === "class_members" || ctx.dataScope.type === "children") {
+    notFound()
+  }
+
+  const summary = await getClassMasterySummary(classId)
+
+  if (!summary) {
+    notFound()
+  }
+
+  return (
+    <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
+      <div>
+        <h2 className="flex items-center gap-2 text-2xl font-bold tracking-tight">
+          <Stethoscope className="h-6 w-6" />
+          Class Diagnostic
+        </h2>
+        <p className="text-muted-foreground">
+          Class-level knowledge point mastery overview and student attention list.
+        </p>
+      </div>
+      <ClassDiagnosticView summary={summary} />
+    </div>
+  )
+}

src/app/(dashboard)/teacher/diagnostic/page.tsx

@@ -0,0 +1,48 @@
+import { getAuthContext } from "@/shared/lib/auth-guard"
+import { getDiagnosticReports } from "@/modules/diagnostic/data-access-reports"
+import { ReportList } from "@/modules/diagnostic/components/report-list"
+import type { DiagnosticReportType, DiagnosticReportStatus } from "@/modules/diagnostic/types"
+
+export const dynamic = "force-dynamic"
+
+type SearchParams = { [key: string]: string | string[] | undefined }
+
+const getParam = (params: SearchParams, key: string) => {
+  const v = params[key]
+  return Array.isArray(v) ? v[0] : v
+}
+
+export default async function TeacherDiagnosticPage({
+  searchParams,
+}: {
+  searchParams: Promise<SearchParams>
+}) {
+  const sp = await searchParams
+  const ctx = await getAuthContext()
+
+  const reportType = getParam(sp, "reportType")
+  const status = getParam(sp, "status")
+
+  const reports = await getDiagnosticReports({
+    reportType: reportType && reportType !== "all" ? (reportType as DiagnosticReportType) : undefined,
+    status: status && status !== "all" ? (status as DiagnosticReportStatus) : undefined,
+  })
+
+  // 学生角色仅查看自己的报告；其他角色查看全部
+  const visibleReports =
+    ctx.dataScope.type === "class_members"
+      ? reports.filter((r) => r.studentId === ctx.userId)
+      : reports
+
+  return (
+    <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
+      <div>
+        <h2 className="text-2xl font-bold tracking-tight">Learning Diagnostic</h2>
+        <p className="text-muted-foreground">
+          View and manage diagnostic reports based on knowledge point mastery.
+        </p>
+      </div>
+      <ReportList reports={visibleReports} />
+    </div>
+  )
+}

src/app/(dashboard)/teacher/diagnostic/student/[studentId]/page.tsx

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+import { notFound } from "next/navigation"
+import { Stethoscope } from "lucide-react"
+import { getAuthContext } from "@/shared/lib/auth-guard"
+import {
+  getStudentMasterySummary,
+  getKnowledgePointStats,
+} from "@/modules/diagnostic/data-access"
+import { getDiagnosticReports } from "@/modules/diagnostic/data-access-reports"
+import { StudentDiagnosticView } from "@/modules/diagnostic/components/student-diagnostic-view"
+import type { MasteryRadarPoint } from "@/modules/diagnostic/types"
+
+export const dynamic = "force-dynamic"
+
+export default async function StudentDiagnosticPage({
+  params,
+}: {
+  params: Promise<{ studentId: string }>
+}) {
+  const { studentId } = await params
+  const ctx = await getAuthContext()
+
+  // DataScope 二次校验：学生只能看自己，家长只能看子女
+  if (ctx.dataScope.type === "class_members" && ctx.userId !== studentId) {
+    notFound()
+  }
+  if (ctx.dataScope.type === "children" && !ctx.dataScope.childrenIds.includes(studentId)) {
+    notFound()
+  }
+
+  const [summary, reports] = await Promise.all([
+    getStudentMasterySummary(studentId),
+    getDiagnosticReports({ studentId }),
+  ])
+
+  // 班级平均掌握度（用于雷达图对比）
+  let classAverageMastery: MasteryRadarPoint[] | undefined
+  if (summary) {
+    // 通过学生所在班级获取班级平均
+    const classStats = await getKnowledgePointStats()
+    classAverageMastery = classStats.map((k) => ({
+      knowledgePoint: k.knowledgePointName,
+      student: 0,
+      classAverage: k.averageMastery,
+    }))
+  }
+
+  return (
+    <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
+      <div>
+        <h2 className="flex items-center gap-2 text-2xl font-bold tracking-tight">
+          <Stethoscope className="h-6 w-6" />
+          Student Diagnostic
+        </h2>
+        <p className="text-muted-foreground">
+          Knowledge point mastery analysis and diagnostic reports.
+        </p>
+      </div>
+      <StudentDiagnosticView
+        summary={summary}
+        reports={reports}
+        classAverageMastery={classAverageMastery}
+      />
+    </div>
+  )
+}

src/app/(dashboard)/teacher/elective/page.tsx

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+import { auth } from "@/auth"
+import { getElectiveCourses } from "@/modules/elective/data-access"
+import { ElectiveCourseList } from "@/modules/elective/components/elective-course-list"
+import type { ElectiveCourseStatus } from "@/modules/elective/types"
+
+export const dynamic = "force-dynamic"
+
+type SearchParams = { [key: string]: string | string[] | undefined }
+
+const getParam = (params: SearchParams, key: string) => {
+  const v = params[key]
+  return Array.isArray(v) ? v[0] : v
+}
+
+const isValidStatus = (v?: string): v is ElectiveCourseStatus =>
+  v === "draft" || v === "open" || v === "closed" || v === "cancelled"
+
+export default async function TeacherElectivePage({
+  searchParams,
+}: {
+  searchParams: Promise<SearchParams>
+}) {
+  const session = await auth()
+  const teacherId = String(session?.user?.id ?? "")
+
+  const sp = await searchParams
+  const statusParam = getParam(sp, "status")
+  const status = isValidStatus(statusParam) ? statusParam : undefined
+
+  const courses = teacherId
+    ? await getElectiveCourses({ teacherId, status })
+    : []
+
+  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">My Elective Courses</h2>
+        <p className="text-muted-foreground">
+          View and manage the elective courses you teach.
+        </p>
+      </div>
+      <ElectiveCourseList
+        courses={courses}
+        canManage
+        createHref="/admin/elective/create"
+        editHrefBuilder={(id) => `/admin/elective/${id}/edit`}
+      />
+    </div>
+  )
+}

src/app/(dashboard)/teacher/exams/[id]/proctoring/page.tsx

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+import { notFound } from "next/navigation"
+import { requirePermission, PermissionDeniedError } from "@/shared/lib/auth-guard"
+import { Permissions } from "@/shared/types/permissions"
+import { ProctoringDashboard } from "@/modules/proctoring/components/proctoring-dashboard"
+import {
+  getExamForProctoring,
+  getExamProctoringSummary,
+  getStudentProctoringStatuses,
+  getRecentProctoringEvents,
+} from "@/modules/proctoring/data-access"
+import type { ProctoringDashboardData } from "@/modules/proctoring/types"
+
+export const dynamic = "force-dynamic"
+
+export default async function ExamProctoringPage({
+  params,
+}: {
+  params: Promise<{ id: string }>
+}) {
+  try {
+    await requirePermission(Permissions.EXAM_PROCTOR)
+  } catch (error) {
+    if (error instanceof PermissionDeniedError) {
+      return (
+        <div className="p-10 text-center text-muted-foreground">
+          您没有监考权限（exam:proctor）。
+        </div>
+      )
+    }
+    throw error
+  }
+
+  const { id } = await params
+  const exam = await getExamForProctoring(id)
+  if (!exam) return notFound()
+
+  // 并行拉取面板初始数据
+  const [summary, students, recentEvents] = await Promise.all([
+    getExamProctoringSummary(id),
+    getStudentProctoringStatuses(id),
+    getRecentProctoringEvents(id, 20),
+  ])
+
+  const initialData: ProctoringDashboardData = {
+    summary,
+    students,
+    recentEvents,
+  }
+
+  return (
+    <div className="flex h-full flex-col space-y-4 p-4">
+      <ProctoringDashboard examId={id} initialData={initialData} />
+    </div>
+  )
+}