下载视频文件

{
    "file": {
        "file_id": "file_abc123",
        "bytes": 5242880,
        "created_at": 1704067200,
        "filename": "video.mp4",
        "purpose": "video_generation",
        "download_url": "https://example.com/download/video.mp4"
    },
    "base_resp": {
        "status_code": 0,
        "status_msg": "success"
    }
}