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/shared/lib/permissions.ts

@@ -47,6 +47,12 @@ export const ROLE_PERMISSIONS: Record<string, Permission[]> = {
     Permissions.MESSAGE_DELETE,
     Permissions.SCHEDULE_AUTO,
     Permissions.SCHEDULE_ADJUST,
+    Permissions.ELECTIVE_MANAGE,
+    Permissions.ELECTIVE_READ,
+    Permissions.EXAM_PROCTOR,
+    Permissions.EXAM_PROCTOR_READ,
+    Permissions.DIAGNOSTIC_MANAGE,
+    Permissions.DIAGNOSTIC_READ,
   ],
   teacher: [
     Permissions.EXAM_CREATE,
@@ -78,6 +84,12 @@ export const ROLE_PERMISSIONS: Record<string, Permission[]> = {
     Permissions.MESSAGE_SEND,
     Permissions.MESSAGE_READ,
     Permissions.MESSAGE_DELETE,
+    Permissions.ELECTIVE_MANAGE,
+    Permissions.ELECTIVE_READ,
+    Permissions.EXAM_PROCTOR,
+    Permissions.EXAM_PROCTOR_READ,
+    Permissions.DIAGNOSTIC_MANAGE,
+    Permissions.DIAGNOSTIC_READ,
   ],
   student: [
     Permissions.EXAM_READ,
@@ -92,6 +104,9 @@ export const ROLE_PERMISSIONS: Record<string, Permission[]> = {
     Permissions.ATTENDANCE_READ,
     Permissions.MESSAGE_READ,
     Permissions.MESSAGE_DELETE,
+    Permissions.ELECTIVE_SELECT,
+    Permissions.ELECTIVE_READ,
+    Permissions.DIAGNOSTIC_READ,
   ],
   parent: [
     Permissions.EXAM_READ,
@@ -135,6 +150,10 @@ export const ROLE_PERMISSIONS: Record<string, Permission[]> = {
     Permissions.MESSAGE_SEND,
     Permissions.MESSAGE_READ,
     Permissions.MESSAGE_DELETE,
+    Permissions.ELECTIVE_READ,
+    Permissions.EXAM_PROCTOR_READ,
+    Permissions.DIAGNOSTIC_MANAGE,
+    Permissions.DIAGNOSTIC_READ,
   ],
   teaching_head: [
     Permissions.EXAM_CREATE,
@@ -163,6 +182,9 @@ export const ROLE_PERMISSIONS: Record<string, Permission[]> = {
     Permissions.MESSAGE_SEND,
     Permissions.MESSAGE_READ,
     Permissions.MESSAGE_DELETE,
+    Permissions.ELECTIVE_READ,
+    Permissions.EXAM_PROCTOR_READ,
+    Permissions.DIAGNOSTIC_READ,
   ],
 }