public record GatewayFleetItem(
    Guid Id,
    string GatewayCode,
    string Department,
    string SiteCode,
    string SiteName,
    string Status,
    int ReportedBufferDepth,
    DateTimeOffset? LastHeartbeatAt,
    DateTimeOffset? LastSyncAt,
    double? MinutesSinceHeartbeat);
