feat(整合): 新增十二项原则页面，支持查看表格与打字填空练习

src/components/layout/Sidebar.tsx

@@ -11,12 +11,14 @@ import {
   ChevronLeft,
   ChevronRight,
   GraduationCap,
+  BookMarked,
 } from 'lucide-react'
 
 const navItems = [
   { path: '/', label: '首页', icon: Home },
   { path: '/process-matrix', label: '49过程矩阵', icon: LayoutGrid },
   { path: '/process-practice', label: '过程背诵练习', icon: GraduationCap },
+  { path: '/principles', label: '十二项原则', icon: BookMarked },
   { path: '/knowledge-areas', label: '知识领域', icon: BookOpen },
   { path: '/process-groups', label: '过程组', icon: Layers },
   { path: '/process-graph', label: '过程关系图', icon: Share2 },