style(导航): 隐藏流程总览图页面入口

- App.tsx 移除 /process-roadmap 路由及组件导入
- 首页功能入口卡片移除"流程总览图"
- 侧边栏导航移除"流程总览图"链接
- ProcessDetailPage 移除"返回总览图"按钮及相关逻辑

via [HAPI](https://hapi.run)

Co-Authored-By: HAPI <noreply@hapi.run>

src/components/layout/Sidebar.tsx

@@ -6,7 +6,6 @@ import {
   BookOpen,
   Layers,
   LayoutGrid,
-  Workflow,
   Share2,
   Settings,
   ChevronLeft,
@@ -16,7 +15,6 @@ import {
 const navItems = [
   { path: '/', label: '首页', icon: Home },
   { path: '/process-matrix', label: '49过程矩阵', icon: LayoutGrid },
-  { path: '/process-roadmap', label: '流程总览图', icon: Workflow },
   { 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 },