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/modules/exams/components/exam-actions.tsx

@@ -155,21 +155,22 @@ export function ExamActions({ exam }: ExamActionsProps) {
   return (
     <>
       <div className="flex items-center gap-1">
-        <Button 
-          variant="ghost" 
-          size="icon" 
+        <Button
+          variant="ghost"
+          size="icon"
           className="h-8 w-8 text-muted-foreground hover:text-foreground"
           onClick={(e) => {
             e.stopPropagation()
             handleView()
           }}
           title="Preview Exam"
+          aria-label="Preview exam"
         >
           <Eye className="h-4 w-4" />
         </Button>
         <DropdownMenu>
           <DropdownMenuTrigger asChild>
-            <Button variant="ghost" className="h-8 w-8 p-0">
+            <Button variant="ghost" className="h-8 w-8 p-0" aria-label="Open menu">
               <span className="sr-only">Open menu</span>
               <MoreHorizontal className="h-4 w-4" />
             </Button>