WebhookPayload_WithdrawalEvent

提现事件通用 payload 结构，适用于以下事件：

withdrawal.success: 提现链上确认成功

withdrawal.rejected: 提现被管理员拒绝

注意: 链上执行失败（内部 FAILED 状态）会自动重试，不推送 webhook。

{
    "eventId": "string",
    "eventType": "withdrawal.success",
    "timestamp": 0,
    "tenantId": 0,
    "data": {
        "orderId": "string",
        "network": "string",
        "currency": "string",
        "toAddress": "string",
        "amount": "string",
        "fee": "string",
        "status": "SUCCESS",
        "txHash": "string",
        "errorMsg": "string"
    }
}