Get Contact Book

{
  "success": true,
  "data": {
    "contactBook": {
      "id": "550e8400-e29b-41d4-a716-446655440000",
      "user_id": "user_uuid",
      "name": "Newsletter Subscribers",
      "contact_count": 142,
      "created_at": "2026-03-07T12:00:00Z",
      "updated_at": "2026-03-07T12:00:00Z"
    }
  }
}