curl -X GET "https://api.nevatal.com/api/v1/billing/invoices?status=approved" \
  -H "Authorization: Bearer nvtl_your_api_key"

{
  "data": [
    {
      "id": "inv_001",
      "invoiceNumber": "FV-2025-0042",
      "patientId": "pat_abc123",
      "patient": {
        "firstName": "María",
        "lastName": "García"
      },
      "status": "approved",
      "subtotal": 150000,
      "tax": 28500,
      "total": 178500,
      "currency": "COP",
      "items": [
        {
          "description": "Consulta General",
          "quantity": 1,
          "unitPrice": 150000,
          "total": 150000
        }
      ],
      "createdAt": "2025-03-15T10:30:00Z",
      "approvedAt": "2025-03-15T11:00:00Z"
    }
  ],
  "pagination": {
    "page": 1,
    "limit": 20,
    "total": 320
  }
}