feat(frontend): 增强用户界面和使用教程

主要改进：
- 扩展 UseKeyModal 支持 Antigravity/Gemini 平台教程
- 添加 CCS (Claude Code Settings) 导入说明
- 添加混合渠道风险警告提示
- 优化登录/注册页面样式
- 更新 Antigravity 混合调度选项文案
- 完善中英文国际化文案

frontend/src/components/layout/AppSidebar.vue

@@ -183,21 +183,6 @@ const DashboardIcon = {
     )
 }
 
-const ActivityIcon = {
-  render: () =>
-    h(
-      'svg',
-      { fill: 'none', viewBox: '0 0 24 24', stroke: 'currentColor', 'stroke-width': '1.5' },
-      [
-        h('path', {
-          'stroke-linecap': 'round',
-          'stroke-linejoin': 'round',
-          d: 'M3 12h4l3 6 4-12 3 6h4'
-        })
-      ]
-    )
-}
-
 const KeyIcon = {
   render: () =>
     h(
@@ -457,7 +442,6 @@ const personalNavItems = computed(() => {
 const adminNavItems = computed(() => {
   const baseItems = [
     { path: '/admin/dashboard', label: t('nav.dashboard'), icon: DashboardIcon },
-    { path: '/admin/ops', label: t('nav.ops'), icon: ActivityIcon },
     { path: '/admin/users', label: t('nav.users'), icon: UsersIcon, hideInSimpleMode: true },
     { path: '/admin/groups', label: t('nav.groups'), icon: FolderIcon, hideInSimpleMode: true },
     { path: '/admin/subscriptions', label: t('nav.subscriptions'), icon: CreditCardIcon, hideInSimpleMode: true },