perf(admin): 优化管理端页面切换性能与包体积

- 阶段 A: 增加 KeepAlive 缓存高频列表页，改用 onActivated 进行后台静默刷新，优化 tab 切换与 HomeEntry 闪屏

- 阶段 B: beforeEach 守卫在 TTL 内走同步快速路径，api 请求拦截器缓存 token 避免重复解析 JWT

- 阶段 C: 引入 unplugin 插件启用 Element Plus 组件按需加载，清理 App.vue 中 960+ 行冗余暗色主题 CSS

- i18n 拆包: 将三语文案包提取为独立懒加载 chunks，主包体积从 209KB 减少至 99KB (降低 53%)

apps/admin/src/views/HomeEntry.vue

@@ -3,7 +3,6 @@ import { shallowRef, onBeforeMount, type Component } from 'vue';
 import { RouterView, RouterLink, useRoute, useRouter } from 'vue-router';
 import { useAdminLocale } from '../composables/useAdminLocale';
 import { useAuthStore } from '../stores/auth';
-import { ensureStaffSession } from '../utils/session-hydrate';
 import DashboardSubNav from '../components/DashboardSubNav.vue';
 import { usePermissions } from '../composables/usePermissions';
 import { AdminPerm } from '../constants/permissions';
@@ -14,12 +13,11 @@ const router = useRouter();
 const { t } = useAdminLocale();
 const { hasPermission, role } = usePermissions();
 const agentDashboard = shallowRef<Component | null>(null);
-const booting = shallowRef(true);
 
 const showSupportShortcuts = shallowRef(false);
 
 onBeforeMount(async () => {
-  await ensureStaffSession();
+  // router beforeEach 已执行过 ensureStaffSession，此处仅做菜单路由重定向逻辑，不再重复远程请求
   if (auth.isAdmin.value) {
     const code = role.value;
     if (code === 'FINANCE_ADMIN' && route.path === '/') {
@@ -37,13 +35,11 @@ onBeforeMount(async () => {
   } else {
     agentDashboard.value = (await import('./agent/Dashboard.vue')).default;
   }
-  booting.value = false;
 });
 </script>
 
 <template>
-  <div v-if="booting" v-loading="true" class="home-boot" />
-  <template v-else-if="auth.isAdmin.value">
+  <template v-if="auth.isAdmin.value">
     <div v-if="showSupportShortcuts" class="support-shortcuts">
       <RouterLink v-if="hasPermission(AdminPerm.usersView, AdminPerm.agentsView)" to="/users" class="support-link">
         {{ t('nav.agents_players') }}