feat(channel): 模型标签输入 + $/MTok 价格单位 + 左开右闭区间 + i18n

- 模型输入改为标签列表（输入回车添加，支持粘贴批量导入）
- 价格显示单位改为 $/MTok（每百万 token），提交时自动转换
- Token 模式增加图片输出价格字段（适配 Gemini 图片模型按 token 计费）
- 区间边界改为左开右闭 (min, max]，右边界包含
- 默认价格作为未命中区间时的回退价格
- 添加完整中英文 i18n 翻译

frontend/src/i18n/locales/en.ts

@@ -335,6 +335,7 @@ export default {
     profile: 'Profile',
     users: 'Users',
     groups: 'Groups',
+    channels: 'Channels',
     subscriptions: 'Subscriptions',
     accounts: 'Accounts',
     proxies: 'Proxies',
@@ -1719,6 +1720,79 @@ export default {
       }
     },
 
+    // Channel Management
+    channels: {
+      title: 'Channel Management',
+      description: 'Manage channels and custom model pricing',
+      searchChannels: 'Search channels...',
+      createChannel: 'Create Channel',
+      editChannel: 'Edit Channel',
+      deleteChannel: 'Delete Channel',
+      statusActive: 'Active',
+      statusDisabled: 'Disabled',
+      allStatus: 'All Status',
+      groupsUnit: 'groups',
+      pricingUnit: 'pricing rules',
+      noChannelsYet: 'No Channels Yet',
+      createFirstChannel: 'Create your first channel to manage model pricing',
+      loadError: 'Failed to load channels',
+      createSuccess: 'Channel created',
+      updateSuccess: 'Channel updated',
+      deleteSuccess: 'Channel deleted',
+      createError: 'Failed to create channel',
+      updateError: 'Failed to update channel',
+      deleteError: 'Failed to delete channel',
+      nameRequired: 'Please enter a channel name',
+      deleteConfirm: 'Are you sure you want to delete channel "{name}"? This cannot be undone.',
+      columns: {
+        name: 'Name',
+        description: 'Description',
+        status: 'Status',
+        groups: 'Groups',
+        pricing: 'Pricing',
+        createdAt: 'Created',
+        actions: 'Actions'
+      },
+      billingMode: {
+        token: 'Token',
+        perRequest: 'Per Request',
+        image: 'Image (Per Request)'
+      },
+      form: {
+        name: 'Name',
+        namePlaceholder: 'Enter channel name',
+        description: 'Description',
+        descriptionPlaceholder: 'Optional description',
+        status: 'Status',
+        groups: 'Associated Groups',
+        noGroupsAvailable: 'No groups available',
+        inOtherChannel: 'In "{name}"',
+        modelPricing: 'Model Pricing',
+        models: 'Models',
+        modelsPlaceholder: 'Type model name and press Enter. Supports wildcard *',
+        modelInputHint: 'Press Enter to add. Supports paste and wildcard *.',
+        billingMode: 'Billing Mode',
+        defaultPrices: 'Default prices (fallback when no interval matches)',
+        inputPrice: 'Input',
+        outputPrice: 'Output',
+        cacheWritePrice: 'Cache Write',
+        cacheReadPrice: 'Cache Read',
+        imageTokenPrice: 'Image Output',
+        imageOutputPrice: 'Image Output Price',
+        pricePlaceholder: 'Default',
+        intervals: 'Context Intervals (optional)',
+        addInterval: 'Add Interval',
+        requestTiers: 'Request Tiers',
+        imageTiers: 'Image Tiers (Per Request)',
+        addTier: 'Add Tier',
+        noTiersYet: 'No tiers yet. Click add to configure per-request pricing.',
+        noPricingRules: 'No pricing rules yet. Click "Add" to create one.',
+        perRequestPrice: 'Price per Request',
+        tierLabel: 'Tier',
+        resolution: 'Resolution'
+      }
+    },
+
     // Subscriptions
     subscriptions: {
       title: 'Subscription Management',