feat(channels): gate available channels behind feature switch (frontend)

Wire the new available_channels_enabled setting end-to-end on the
frontend — hide the user sidebar entry by default and surface the
toggle under Admin Settings > Features.

- types/PublicSettings + api/admin/settings SystemSettings +
  UpdateSettingsRequest: add available_channels_enabled
- stores/app cached fallback: available_channels_enabled: false
- AppSidebar: add flagAvailableChannels getter (strict === true:
  default hide), apply to /available-channels nav entry
- SettingsView: Features tab — new Toggle card, form default/payload
- i18n (zh/en): admin.settings.features.availableChannels.*

frontend/src/api/admin/settings.ts

@@ -148,6 +148,9 @@ export interface SystemSettings {
   // Channel Monitor feature switch
   channel_monitor_enabled: boolean
   channel_monitor_default_interval_seconds: number
+
+  // Available Channels feature switch
+  available_channels_enabled: boolean
 }
 
 export interface UpdateSettingsRequest {
@@ -259,6 +262,9 @@ export interface UpdateSettingsRequest {
   // Channel Monitor feature switch
   channel_monitor_enabled?: boolean
   channel_monitor_default_interval_seconds?: number
+
+  // Available Channels feature switch
+  available_channels_enabled?: boolean
 }
 
 /**

frontend/src/components/layout/AppSidebar.vue

@@ -631,6 +631,9 @@ const ChevronDownIcon = {
 // getter 返回 false = 隐藏；undefined/true = 显示（宽容策略，避免 public settings 未加载闪烁）。
 const flagChannelMonitor = () => appStore.cachedPublicSettings?.channel_monitor_enabled
 const flagPayment = () => appStore.cachedPublicSettings?.payment_enabled
+// Opt-in feature：默认关闭，未加载 settings 时也视为关闭（严格 === true 判定）
+const flagAvailableChannels = () =>
+  appStore.cachedPublicSettings?.available_channels_enabled === true
 const flagOpsMonitoring = () => adminSettingsStore.opsMonitoringEnabled
 const flagAdminPayment = () => adminSettingsStore.paymentEnabled
 
@@ -648,7 +651,7 @@ function buildSelfNavItems(withDashboard: boolean): NavItem[] {
     { path: '/subscriptions', label: t('nav.mySubscriptions'), icon: CreditCardIcon, hideInSimpleMode: true },
     { path: '/purchase', label: t('nav.buySubscription'), icon: RechargeSubscriptionIcon, hideInSimpleMode: true, featureFlag: flagPayment },
     { path: '/orders', label: t('nav.myOrders'), icon: OrderListIcon, hideInSimpleMode: true, featureFlag: flagPayment },
-    { path: '/available-channels', label: t('nav.availableChannels'), icon: ChannelIcon, hideInSimpleMode: true },
+    { path: '/available-channels', label: t('nav.availableChannels'), icon: ChannelIcon, hideInSimpleMode: true, featureFlag: flagAvailableChannels },
     { path: '/redeem', label: t('nav.redeem'), icon: GiftIcon, hideInSimpleMode: true },
     { path: '/profile', label: t('nav.profile'), icon: UserIcon },
     ...customMenuItemsForUser.value.map((item): NavItem => ({

frontend/src/i18n/locales/en.ts

@@ -4541,6 +4541,12 @@ export default {
           defaultInterval: 'Default check interval (seconds)',
           defaultIntervalHint: 'Pre-fills the interval when creating a new monitor; each monitor can override it. Range 15 – 3600.',
         },
+        availableChannels: {
+          title: 'Available Channels',
+          description: 'Show logged-in users an aggregate view of the channels, models and pricing they can access. Disabled by default.',
+          enabled: 'Enable Available Channels',
+          enabledHint: 'When off, the sidebar entry is hidden and the endpoint returns an empty list.',
+        },
       },
       emailTabDisabledTitle: 'Email Verification Not Enabled',
       emailTabDisabledHint: 'Enable email verification in the Security tab to configure SMTP settings.',

frontend/src/i18n/locales/zh.ts

@@ -4714,6 +4714,12 @@ export default {
           defaultInterval: '默认检测间隔（秒）',
           defaultIntervalHint: '新建渠道监控时表单的默认值，可被单个渠道覆盖。范围 15 – 3600 秒。',
         },
+        availableChannels: {
+          title: '可用渠道',
+          description: '向已登录用户展示他们能访问的渠道、模型和定价聚合视图。默认关闭。',
+          enabled: '启用可用渠道',
+          enabledHint: '关闭后用户端侧边栏入口隐藏，接口返回空数组。',
+        },
       },
       emailTabDisabledTitle: '邮箱验证未启用',
       emailTabDisabledHint: '请在「安全与认证」选项卡中启用邮箱验证后，再配置 SMTP 设置。',

frontend/src/stores/app.ts

@@ -345,6 +345,7 @@ export const useAppStore = defineStore('app', () => {
         balance_low_notify_threshold: 0,
         channel_monitor_enabled: true,
         channel_monitor_default_interval_seconds: 60,
+        available_channels_enabled: false,
       }
     }
 

frontend/src/types/index.ts

@@ -132,6 +132,7 @@ export interface PublicSettings {
   balance_low_notify_threshold: number
   channel_monitor_enabled: boolean
   channel_monitor_default_interval_seconds: number
+  available_channels_enabled: boolean
 }
 
 export interface AuthResponse {

frontend/src/views/admin/SettingsView.vue

@@ -2416,6 +2416,30 @@
           </div>
         </div>
 
+        <div class="card">
+          <div class="border-b border-gray-100 px-6 py-4 dark:border-dark-700">
+            <h2 class="text-lg font-semibold text-gray-900 dark:text-white">
+              {{ t('admin.settings.features.availableChannels.title') }}
+            </h2>
+            <p class="mt-1 text-sm text-gray-500 dark:text-gray-400">
+              {{ t('admin.settings.features.availableChannels.description') }}
+            </p>
+          </div>
+          <div class="space-y-5 p-6">
+            <div class="flex items-center justify-between">
+              <div>
+                <label class="text-sm font-medium text-gray-700 dark:text-gray-300">
+                  {{ t('admin.settings.features.availableChannels.enabled') }}
+                </label>
+                <p class="mt-0.5 text-xs text-gray-500 dark:text-gray-400">
+                  {{ t('admin.settings.features.availableChannels.enabledHint') }}
+                </p>
+              </div>
+              <Toggle v-model="form.available_channels_enabled" />
+            </div>
+          </div>
+        </div>
+
         </div><!-- /Tab: Features -->
 
         <!-- Tab: Email -->
@@ -3145,7 +3169,9 @@ const form = reactive<SettingsForm>({
   account_quota_notify_emails: [] as NotifyEmailEntry[],
   // Channel Monitor feature switch
   channel_monitor_enabled: true,
-  channel_monitor_default_interval_seconds: 60
+  channel_monitor_default_interval_seconds: 60,
+  // Available Channels feature switch
+  available_channels_enabled: false
 })
 
 // Proxies for web search emulation ProxySelector
@@ -3749,6 +3775,8 @@ async function saveSettings() {
       // Channel Monitor feature switch
       channel_monitor_enabled: form.channel_monitor_enabled,
       channel_monitor_default_interval_seconds: Number(form.channel_monitor_default_interval_seconds) || 60,
+      // Available Channels feature switch
+      available_channels_enabled: form.available_channels_enabled,
     }
 
     const updated = await adminAPI.settings.updateSettings(payload)