feat(channels): 模型定价支持一键同步最新模型

从 LiteLLM 定价目录中读取指定平台的最新模型列表，
将尚未录入的模型以新定价条目（价格留空）的形式追加，
管理员只需点击同步最新模型按钮即可完成操作。

- backend/service: PricingService 新增 ListModelNamesByProvider
- backend/handler: ChannelHandler 新增 SyncPricingModels (GET /api/v1/admin/channels/pricing/sync-models)
- backend/routes: 注册新路由（在 /:id 通配符之前）
- backend/wire_gen: 手动更新 NewChannelHandler 调用
- frontend/api: channels.ts 新增 syncPricingModels
- frontend/i18n: zh.ts / en.ts 新增 5 个 key
- frontend/view: ChannelsView 定价区域标题行新增「同步最新模型」按钮
- tests: pricing_service_test + channel_handler_test 新增单元测试

frontend/src/api/admin/channels.ts

@@ -164,5 +164,19 @@ export async function getModelDefaultPricing(model: string): Promise<ModelDefaul
   return data
 }
 
-const channelsAPI = { list, getById, create, update, remove, getModelDefaultPricing }
+export interface SyncPricingModelsResult {
+  models: string[]
+}
+
+/**
+ * Fetch the latest model names from the LiteLLM pricing catalog for the given platform
+ */
+export async function syncPricingModels(platform: string): Promise<SyncPricingModelsResult> {
+  const { data } = await apiClient.get<SyncPricingModelsResult>('/admin/channels/pricing/sync-models', {
+    params: { platform }
+  })
+  return data
+}
+
+const channelsAPI = { list, getById, create, update, remove, getModelDefaultPricing, syncPricingModels }
 export default channelsAPI