refactor: 统一接口调用为单前缀写法，去除 19 处页面内写死的 /mp-api（API_BASE 已含），并新增 check:api-prefix 防回归脚本

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/packages/user/api/douyin.ts

@@ -82,7 +82,7 @@ export async function queryVoucherList(params: QueryVoucherListParams): Promise<
     await delay(300)
     return MOCK_VOUCHERS.map((v) => ({ ...v, mobile: params.mobile }))
   }
-  return post<VoucherItem[]>('/mp-api/douyin/voucherList', params)
+  return post<VoucherItem[]>('/douyin/voucherList', params)
 }
 
 /**
@@ -94,5 +94,5 @@ export async function activateAndBind(params: ActivateAndBindParams): Promise<vo
     await delay(800)
     return
   }
-  await post<null>('/mp-api/douyin/activateAndBind', params)
+  await post<null>('/douyin/activateAndBind', params)
 }