fix(fin): 补全提现审批人字段 FIN-01

- Approve updates map 补充 approved_by 和 approved_at 字段，确保审批人信息正确填充

internal/service/commission_withdrawal/service.go

@@ -206,6 +206,8 @@ func (s *Service) Approve(ctx context.Context, id uint, req *dto.ApproveWithdraw
 			"processed_at": now,
 			"payment_type": req.PaymentType,
 			"remark":       req.Remark,
+			"approved_by":  currentUserID,
+			"approved_at":  now,
 		}
 
 		if req.Amount != nil {