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

service/error.go

@@ -206,3 +206,16 @@ func TaskErrorWrapper(err error, code string, statusCode int) *dto.TaskError {
 
 	return taskError
 }
+
+// TaskErrorFromAPIError 将 PreConsumeBilling 返回的 NewAPIError 转换为 TaskError。
+func TaskErrorFromAPIError(apiErr *types.NewAPIError) *dto.TaskError {
+	if apiErr == nil {
+		return nil
+	}
+	return &dto.TaskError{
+		Code:       string(apiErr.GetErrorCode()),
+		Message:    apiErr.Err.Error(),
+		StatusCode: apiErr.StatusCode,
+		Error:      apiErr.Err,
+	}
+}