Need to Update and Unify Appearance of GUI across operating systems (Windows, Mac, Linux)

[CodeByDrescher]

While originally we had a unified appearance for each operating system, over time we've let the appearance fall by the wayside, even as "dark mode" became featured in operating systems.

Now, with accessibility requirements becoming a priority, we need to create a centralized, unified appearance, both light and dark, across OS types, in order to make sure when we develop on one OS, we can be reasonably sure that it works on all OS and "light" types.