task-7(壳层/路由): 根路由跳转到首个可见页面，移除硬编码默认页

helpers.firstVisiblePath 深度优先返回首个可路由页面，无页面返回空串；
store 增加 firstVisible；守卫在根路由/无权限时跳首个可见页，全部无页面则
停留根路由展示无菜单空态，删除 redirect:'/account/users' 硬编码。

admin-frontend-vue/src/router/index.ts

@@ -2,7 +2,6 @@ import { createRouter, createWebHistory } from 'vue-router'
 import type { AdminMenuNode } from '@/types/admin'
 import AdminLayout from '@/layout/AdminLayout.vue'
 import { useAdminSessionStore } from '@/stores/admin-session'
-import { findFirstRoute } from './helpers'
 import { APP_BASE_PATH } from '@/config/app'
 
 const router = createRouter({
@@ -12,7 +11,6 @@ const router = createRouter({
       path: '/',
       component: AdminLayout,
       children: [
-        { path: '', redirect: '/account/users' },
         { path: 'account/users', component: () => import('@/pages/account/UsersPage.vue'), meta: { menuKey: 'admin_users', title: '用户管理' } },
         { path: 'account/menus', component: () => import('@/pages/account/MenusPage.vue'), meta: { menuKey: 'admin_columns', title: '菜单管理' } },
         { path: 'account/groups', component: () => import('@/pages/account/GroupsPage.vue'), meta: { menuKey: 'admin_group_manage', title: '数据权限分组' } },
@@ -30,10 +28,14 @@ router.beforeEach(async (to) => {
       return false
     }
   }
-  if (to.path === '/') return findFirstRoute(session.menuTree)
+  // 根路由：有可见页面时跳到首个可见页；没有任何页面时停留根路由展示无菜单空态。
+  if (to.path === '/') {
+    return session.firstVisible || true
+  }
   const menuKey = to.meta.menuKey as string | undefined
   if (menuKey && !session.isSuperAdmin && !hasMenu(session.menuTree, menuKey)) {
-    return findFirstRoute(session.menuTree)
+    // 无权限页面：回退到首个可见页面；一个都没有则回根路由空态。
+    return session.firstVisible || '/'
   }
   return true
 })
@@ -43,6 +45,3 @@ function hasMenu(nodes: AdminMenuNode[], key: string): boolean {
 }
 
 export default router
-
-
-