refactor(task): extract billing and polling logic from controller to service layer

Restructure the task relay system for better separation of concerns:
- Extract task billing into service/task_billing.go with unified settlement flow
- Move task polling loop from controller to service/task_polling.go (supports Suno + video platforms)
- Split RelayTask into fetch/submit paths with dedicated retry logic (taskSubmitWithRetry)
- Add TaskDto, TaskResponse generics, and FetchReq to dto/task.go
- Add taskcommon/helpers.go for shared task adaptor utilities
- Remove controller/task_video.go (logic consolidated into service layer)
- Update all task adaptors (ali, doubao, gemini, hailuo, jimeng, kling, sora, suno, vertex, vidu)
- Simplify frontend task logs to use new TaskDto response format

relay/helper/price.go

@@ -140,7 +140,7 @@ func ModelPriceHelper(c *gin.Context, info *relaycommon.RelayInfo, promptTokens
 }
 
 // ModelPriceHelperPerCall 按次计费的 PriceHelper (MJ、Task)
-func ModelPriceHelperPerCall(c *gin.Context, info *relaycommon.RelayInfo) types.PerCallPriceData {
+func ModelPriceHelperPerCall(c *gin.Context, info *relaycommon.RelayInfo) types.PriceData {
 	groupRatioInfo := HandleGroupRatio(c, info)
 
 	modelPrice, success := ratio_setting.GetModelPrice(info.OriginModelName, true)
@@ -154,7 +154,18 @@ func ModelPriceHelperPerCall(c *gin.Context, info *relaycommon.RelayInfo) types.
 		}
 	}
 	quota := int(modelPrice * common.QuotaPerUnit * groupRatioInfo.GroupRatio)
-	priceData := types.PerCallPriceData{
+
+	// 免费模型检测（与 ModelPriceHelper 对齐）
+	freeModel := false
+	if !operation_setting.GetQuotaSetting().EnableFreeModelPreConsume {
+		if groupRatioInfo.GroupRatio == 0 || modelPrice == 0 {
+			quota = 0
+			freeModel = true
+		}
+	}
+
+	priceData := types.PriceData{
+		FreeModel:      freeModel,
 		ModelPrice:     modelPrice,
 		Quota:          quota,
 		GroupRatioInfo: groupRatioInfo,