Create Material Asset Group

curl https://api.aisonar.dev/v1/videos/assets/groups \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"library_type":"aigc_avatar","group_name":"Product references","description":"Reusable product shots"}'

{
  "id": "group-20260720123456-vrt01",
  "object": "seedance.material_asset_group",
  "library_type": "aigc_avatar",
  "group_name": "Product references",
  "description": "Reusable product shots",
  "status": "ACTIVE",
  "metadata": null,
  "created_at": 1782998400000
}