追加上传到已有素材组

{
  "data": {
    "group": {
      "groupId": "group_xxx",
      "groupName": "产品素材组",
      "displayName": "产品素材组",
      "groupType": "AIGC"
    },
    "assets": [
      {
        "fileName": "image.png",
        "assetName": "image.png",
        "assetType": "Image",
        "assetId": "asset_xxx",
        "assetUrl": "https://example.com/path/to/asset.png",
        "coverUrl": "https://example.com/path/to/asset.png",
        "status": "SUCCESS",
        "createdTime": "2026-06-30T00:00:00Z"
      }
    ]
  },
  "error": {
    "code": "not_found",
    "message": "asset group not found"
  },
  "request_id": "req_xxx"
}

{
  "data": null,
  "error": {
    "code": "not_found",
    "message": "asset group not found"
  },
  "request_id": "req_xxx"
}