MerchantApiResponse 统一响应结构。
{
"code": 0,
"message": "成功",
"data": {
"projectId": "2016422018623922178",
"platformUserId": "DY20260115105692",
"maskedPhone": "138****5678",
"accepted": true,
"message": "签约链接已生成",
"errorCode": 0,
"taskId": "2034454171060154370",
"makerId": "2034454171060154371",
"url": "https://sign.example.com/sign?token=3f2d8d44a8c34973a7359b6057f5fd5f"
},
"timestamp": 1742891000000,
"requestId": "req_xxx",
"encrypted": false,
"encryptedData": null,
"signature": "xxxx"
}