refactor: RBAC权限系统重构 + UI组件拆分 + 测试修复 + 架构文档

- RBAC: 新增30个权限点、DataScope行级权限、requirePermission守卫，所有57+ Server Action接入权限校验
- UI拆分: exam-form(1623行→11文件)、textbook-reader(744行→7文件)，均降至300行以内
- 测试: 新增5个单元测试文件(19用例)，修复4个集成测试文件(38用例全部通过)
- 架构文档: 新增架构影响地图(004/005)、标准功能清单(006)、差距审计报告(007)
- 项目规则: 架构图优先规则，改码必同步图
- 安全: rehype-sanitize净化、AES加密API Key、权限路由守卫
- 无障碍: skip-link、aria-label、prefers-reduced-motion
- 性能: next/font优化、next/image、代码分割

src/app/(dashboard)/profile/page.tsx

@@ -9,6 +9,7 @@ import { StudentTodayScheduleCard } from "@/modules/dashboard/components/student
 import { StudentUpcomingAssignmentsCard } from "@/modules/dashboard/components/student-dashboard/student-upcoming-assignments-card"
 import { getStudentDashboardGrades, getStudentHomeworkAssignments } from "@/modules/homework/data-access"
 import { getUserProfile } from "@/modules/users/data-access"
+import { Permissions } from "@/shared/types/permissions"
 import { Badge } from "@/shared/components/ui/badge"
 import { Button } from "@/shared/components/ui/button"
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from "@/shared/components/ui/card"
@@ -42,9 +43,9 @@ export default async function ProfilePage() {
       redirect("/login")
   }
 
-  const role = userProfile.role || "student"
-  const isStudent = role === "student"
-  const isTeacher = role === "teacher"
+  const permissions = session.user.permissions ?? []
+  const isStudent = permissions.includes(Permissions.HOMEWORK_SUBMIT) && !permissions.includes(Permissions.EXAM_CREATE)
+  const isTeacher = permissions.includes(Permissions.EXAM_CREATE)
 
   const studentData =
     isStudent