CSS light / dark mode #4

I hope you don't mind if I open another issue :)

The @media (prefers-color-scheme: light) CSS patterns don't appear to function properly in the widget. They work in the preview within the app, but if I refresh the widget directly, I always end up with the dark mode version, no matter what I have configured in iOS.

If this was working, then another step would be to auto-refresh each widget on a light-dark-mode change, so that the color can actually match. Or, to be more responsive (as in, swap colors immediately), the widget could also be rendered in light mode and dark mode every time, such that the image can be swapped quickly when needed. To avoid this from increasing the load times of widgets, the second (opposite) color scheme could be rendered after the current one has been, which can then already be presented.