Listar webhooks

{  "success": true,  "webhooks": {    "campaign_status_url": "http://example.com",    "campaign_progress_url": "http://example.com",    "channel_status_url": "http://example.com"  }}

{  "success": false,  "error": "Unauthorized",  "message": "Chave de API inválida ou ausente."}

{  "success": false,  "error": "Internal Server Error",  "message": "Erro interno ao processar a requisição."}