同步等待

POST https://qingbo.dev/v1/tasks/sync

{
  "task_id": "task_xxx",
  "model": "gpt-4o-image",
  "status": "completed",
  "created_at": 1720000000,
  "completed_at": 1720000010,
  "progress": 100,
  "result": {
    "images": [
      { "url": "https://...", "expires_at": 1720086400 }
    ]
  }
}

{
  "task_id": "task_xxx",
  "status": "processing",
  "progress": 45,
  "poll_url": "/v1/tasks/task_xxx"
}