Check the status of a HeyGen avatar video generation task (single check)

This endpoint:

1. Retrieves the task from the database
2. Checks the current status with HeyGen API (single check, no polling)
3. Updates the task status based on the response
4. Returns video URLs (video_url, thumbnail_url, video_url_caption) when completed

Args: task_id: The internal task ID (UUID) returned from the create endpoint

Returns: dict with status and data: - status: "In Progress", "Done", or "Error" - data: Contains video_url, thumbnail_url, video_url_caption when completed

Note: This endpoint checks the status once and returns immediately. The client should poll this endpoint if they need to wait for completion.