fix(task): attribute async task usage log to the initiating node (#5684)

Async task usage logs (LogQuotaData node dimension) were recorded
under whichever node happened to poll the task to completion, not the
node that submitted it. For token/adaptor-billed video tasks the
pre-deduction is often 0, so the entire quota landed on the last
polling node.

Snapshot common.NodeName into TaskPrivateData at submit time and use
it when writing the settlement consume log; fall back to the current
node when empty so existing tasks stay compatible.

model/task.go

@@ -104,6 +104,7 @@ type TaskPrivateData struct {
 	BillingSource  string              `json:"billing_source,omitempty"`  // "wallet" 或 "subscription"
 	SubscriptionId int                 `json:"subscription_id,omitempty"` // 订阅 ID，用于订阅退款
 	TokenId        int                 `json:"token_id,omitempty"`        // 令牌 ID，用于令牌额度退款
+	NodeName       string              `json:"node_name,omitempty"`       // 发起任务的节点名，轮询结算阶段据此归属日志而非最后查询节点
 	BillingContext *TaskBillingContext `json:"billing_context,omitempty"` // 计费参数快照（用于轮询阶段重新计算）
 }