feat(task): add model redirection, per-call billing, and multipart retry fix for async tasks

1. Async task model redirection (aligned with sync tasks):
   - Integrate ModelMappedHelper in RelayTaskSubmit after model name
     determination, populating OriginModelName / UpstreamModelName on RelayInfo.
   - All task adaptors now send UpstreamModelName to upstream providers:
     - Gemini & Vertex: BuildRequestURL uses UpstreamModelName.
     - Doubao & Ali: BuildRequestBody conditionally overwrites body.Model.
     - Vidu, Kling, Hailuo, Jimeng: convertToRequestPayload accepts RelayInfo
       and unconditionally uses info.UpstreamModelName.
     - Sora: BuildRequestBody parses JSON and multipart bodies to replace
       the "model" field with UpstreamModelName.
   - Frontend log visibility: LogTaskConsumption and taskBillingOther now
     emit is_model_mapped / upstream_model_name in the "other" JSON field.
   - Billing safety: RecalculateTaskQuotaByTokens reads model name from
     BillingContext.OriginModelName (via taskModelName) instead of
     task.Data["model"], preventing billing leaks from upstream model names.

2. Per-call billing (TaskPricePatches lifecycle):
   - Rename TaskBillingContext.ModelName → OriginModelName; add PerCallBilling
     bool field, populated from TaskPricePatches at submission time.
   - settleTaskBillingOnComplete short-circuits when PerCallBilling is true,
     skipping both adaptor adjustments and token-based recalculation.
   - Remove ModelName from TaskSubmitResult; use relayInfo.OriginModelName
     consistently in controller/relay.go for billing context and logging.

3. Multipart retry boundary mismatch fix:
   - Root cause: after Sora (or OpenAI audio) rebuilds a multipart body with a
     new boundary and overwrites c.Request.Header["Content-Type"], subsequent
     calls to ParseMultipartFormReusable on retry would parse the cached
     original body with the wrong boundary, causing "NextPart: EOF".
   - Fix: ParseMultipartFormReusable now caches the original Content-Type in
     gin context key "_original_multipart_ct" on first call and reuses it for
     all subsequent parses, making multipart parsing retry-safe globally.
   - Sora adaptor reverted to the standard pattern (direct header set/get),
     which is now safe thanks to the root fix.

4. Tests:
   - task_billing_test.go: update makeTask to use OriginModelName; add
     PerCallBilling settlement tests (skip adaptor adjust, skip token recalc);
     add non-per-call adaptor adjustment test with refund verification.

service/task_billing.go

@@ -16,11 +16,11 @@ import (
 
 // LogTaskConsumption 记录任务消费日志和统计信息（仅记录，不涉及实际扣费）。
 // 实际扣费已由 BillingSession（PreConsumeBilling + SettleBilling）完成。
-func LogTaskConsumption(c *gin.Context, info *relaycommon.RelayInfo, modelName string) {
+func LogTaskConsumption(c *gin.Context, info *relaycommon.RelayInfo) {
 	tokenName := c.GetString("token_name")
 	logContent := fmt.Sprintf("操作 %s", info.Action)
 	// 支持任务仅按次计费
-	if common.StringsContains(constant.TaskPricePatches, modelName) {
+	if common.StringsContains(constant.TaskPricePatches, info.OriginModelName) {
 		logContent = fmt.Sprintf("%s，按次计费", logContent)
 	} else {
 		if len(info.PriceData.OtherRatios) > 0 {
@@ -42,9 +42,13 @@ func LogTaskConsumption(c *gin.Context, info *relaycommon.RelayInfo, modelName s
 	if info.PriceData.GroupRatioInfo.HasSpecialRatio {
 		other["user_group_ratio"] = info.PriceData.GroupRatioInfo.GroupSpecialRatio
 	}
+	if info.IsModelMapped {
+		other["is_model_mapped"] = true
+		other["upstream_model_name"] = info.UpstreamModelName
+	}
 	model.RecordConsumeLog(c, info.UserId, model.RecordConsumeLogParams{
 		ChannelId: info.ChannelId,
-		ModelName: modelName,
+		ModelName: info.OriginModelName,
 		TokenName: tokenName,
 		Quota:     info.PriceData.Quota,
 		Content:   logContent,
@@ -120,13 +124,18 @@ func taskBillingOther(task *model.Task) map[string]interface{} {
 			}
 		}
 	}
+	props := task.Properties
+	if props.UpstreamModelName != "" && props.UpstreamModelName != props.OriginModelName {
+		other["is_model_mapped"] = true
+		other["upstream_model_name"] = props.UpstreamModelName
+	}
 	return other
 }
 
 // taskModelName 从 BillingContext 或 Properties 中获取模型名称。
 func taskModelName(task *model.Task) string {
-	if bc := task.PrivateData.BillingContext; bc != nil && bc.ModelName != "" {
-		return bc.ModelName
+	if bc := task.PrivateData.BillingContext; bc != nil && bc.OriginModelName != "" {
+		return bc.OriginModelName
 	}
 	return task.Properties.OriginModelName
 }
@@ -237,15 +246,7 @@ func RecalculateTaskQuotaByTokens(ctx context.Context, task *model.Task, totalTo
 		return
 	}
 
-	// 获取模型名称
-	var taskData map[string]interface{}
-	if err := common.Unmarshal(task.Data, &taskData); err != nil {
-		return
-	}
-	modelName, ok := taskData["model"].(string)
-	if !ok || modelName == "" {
-		return
-	}
+	modelName := taskModelName(task)
 
 	// 获取模型价格和倍率
 	modelRatio, hasRatioSetting, _ := ratio_setting.GetModelRatio(modelName)