scale method
Scale value based on device type.
Uses configurable scale factors (default: mobile 1x, tablet 1.2x, desktop 1.5x).
Implementation
double scale(double value) {
final config = _config;
if (isDesktop) return value * config.desktopScaleFactor;
if (isTablet) return value * config.tabletScaleFactor;
return value * config.mobileScaleFactor;
}