用字典（键：task_id，值：asyncio.Task 对象）维护 “活跃轮询任务” 的映射关系，实现 “任务注册 - 查询 - 注销” 

用信号量（Semaphore）限制并发数

async with self.semaphore:
    while True:
        if datetime.now() - start_time > timedelta(seconds=self.task_timeout):
            task = await TranscriptionTask.get_by_id(self.db, task_id)
            if task:
                await task.mark_as_completed(
                    self.db, 
                    result_text=f"任务超时 (超过{self.task_timeout}秒)", 
                    task_status="FAILED"
                )
            break

        transcribe_response = Transcription.fetch(task=asr_task_id)
        task_status = transcribe_response.output.task_status

        if task_status != last_status:
            last_status = task_status

        if task_status == 'PENDING':
            current_interval = await self._handle_pending_status(task_id, current_interval)
            await asyncio.sleep(current_interval)
        elif task_status == 'RUNNING':
            current_interval = await self._handle_running_status(task_id, current_interval)
            await asyncio.sleep(current_interval)
        elif task_status == 'SUCCEEDED':
            results = transcribe_response.output.results[0] if transcribe_response.output.results else None
            if await self._handle_succeeded_status(task_id, asr_task_id, local_file_path, results):
                break