List contacts (paginated)

{
    "contacts": [
        {
            "id": "co1a2b3c-d4e5-6789-abcd-ef1234567890",
            "email": "john@example.com",
            "firstName": "John",
            "lastName": "Doe",
            "phone": "+1234567890",
            "country": "US",
            "firstDownloadAt": "2026-02-15T10:30:00.000Z",
            "lastDownloadAt": "2026-03-20T08:15:00.000Z",
            "totalDownloads": 5
        }
    ],
    "pagination": {
        "page": 1,
        "limit": 50,
        "total": 128,
        "totalPages": 3
    }
}