fix: mark task settlement logs with is_task for tiered billing display (#7446)

Author: feitianbubu

service/task_billing.go

@@ -147,6 +147,8 @@ func taskAdjustTokenQuota(ctx context.Context, task *model.Task, delta int) {
 // taskBillingOther 从 task 的 BillingContext 构建日志 Other 字段。
 func taskBillingOther(task *model.Task) *model.LogOther {
 	other := model.NewLogOther()
+	// 前端列表按 is_task 选择任务档位渲染分支,缺失会把差额/退款日志误判成普通 relay 动态计费
+	other.SetPublic("is_task", true)
 	if bc := task.PrivateData.BillingContext; bc != nil {
 		other.SetPublic("model_price", bc.ModelPrice)
 		if bc.ModelRatio > 0 {