fix: 修复 Gateway 流量卡接口路径、响应模型和时间戳与上游文档不一致

- 时间戳从 UnixMilli (13位) 改为 Unix (10位秒级)
- 实名状态接口路径 /realname-status → /realName
- 实名链接接口路径 /realname-link → /RealNameVerification
- RealnameStatusResp: status string → realStatus bool + iccid
- FlowUsageResp: usedFlow int64 → used float64 + iccid
- RealnameLinkResp: link → url

internal/gateway/client.go

@@ -72,7 +72,7 @@ func (c *Client) doRequest(ctx context.Context, path string, businessData interf
 		return nil, err
 	}
 
-	timestamp := time.Now().UnixMilli()
+	timestamp := time.Now().Unix()
 	sign := generateSign(c.appID, encryptedData, timestamp, c.appSecret)
 
 	reqBody := map[string]interface{}{