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/exams/[id]/proctoring/page.tsx

@@ -0,0 +1,55 @@
+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>
+  )
+}