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/modules/layout/config/navigation.ts

@@ -16,7 +16,9 @@ import {
   GraduationCap,
   Mail,
   CalendarCheck,
-  CalendarClock
+  CalendarClock,
+  Stethoscope,
+  BookMarked
 } from "lucide-react"
 import type { LucideIcon } from "lucide-react"
 import { Permissions } from "@/shared/types/permissions"
@@ -83,6 +85,12 @@ export const NAV_CONFIG: Record<Role, NavItem[]> = {
       href: "/admin/announcements",
       permission: Permissions.ANNOUNCEMENT_MANAGE,
     },
+    {
+      title: "Electives",
+      icon: BookMarked,
+      href: "/admin/elective",
+      permission: Permissions.ELECTIVE_MANAGE,
+    },
     {
       title: "Messages",
       icon: Mail,
@@ -180,6 +188,18 @@ export const NAV_CONFIG: Record<Role, NavItem[]> = {
       href: "/teacher/schedule-changes",
       permission: Permissions.SCHEDULE_ADJUST,
     },
+    {
+      title: "Diagnostic",
+      icon: Stethoscope,
+      href: "/teacher/diagnostic",
+      permission: Permissions.DIAGNOSTIC_READ,
+    },
+    {
+      title: "Electives",
+      icon: BookMarked,
+      href: "/teacher/elective",
+      permission: Permissions.ELECTIVE_MANAGE,
+    },
     {
       title: "Management",
       icon: Briefcase,
@@ -238,6 +258,18 @@ export const NAV_CONFIG: Record<Role, NavItem[]> = {
       href: "/student/attendance",
       permission: Permissions.ATTENDANCE_READ,
     },
+    {
+      title: "Diagnostic",
+      icon: Stethoscope,
+      href: "/student/diagnostic",
+      permission: Permissions.DIAGNOSTIC_READ,
+    },
+    {
+      title: "Electives",
+      icon: BookMarked,
+      href: "/student/elective",
+      permission: Permissions.ELECTIVE_SELECT,
+    },
     {
       title: "Announcements",
       icon: Megaphone,