feat(account): 账号测试支持选择模型

- 新增 GET /api/v1/admin/accounts/:id/models 接口获取账号可用模型
- 账号测试弹窗新增模型选择下拉框
- 测试时支持传入 model_id 参数，不传则默认使用 Sonnet
- API Key 账号支持根据 model_mapping 映射测试模型
- 将模型常量提取到 claude 包统一管理

frontend/src/api/admin/accounts.ts

@@ -11,6 +11,7 @@ import type {
   PaginatedResponse,
   AccountUsageInfo,
   WindowStats,
+  ClaudeModel,
 } from '@/types';
 
 /**
@@ -247,6 +248,16 @@ export async function setSchedulable(id: number, schedulable: boolean): Promise<
   return data;
 }
 
+/**
+ * Get available models for an account
+ * @param id - Account ID
+ * @returns List of available models for this account
+ */
+export async function getAvailableModels(id: number): Promise<ClaudeModel[]> {
+  const { data } = await apiClient.get<ClaudeModel[]>(`/admin/accounts/${id}/models`);
+  return data;
+}
+
 export const accountsAPI = {
   list,
   getById,
@@ -262,6 +273,7 @@ export const accountsAPI = {
   getTodayStats,
   clearRateLimit,
   setSchedulable,
+  getAvailableModels,
   generateAuthUrl,
   exchangeCode,
   batchCreate,