[Feature] Rework the (dark mode) design

The feature Hi, thanks for the awesome app. As I am not a designer by myself I can provide limited help on this topic. However there is a fundamental issue at the moment with the design of immich from my point of view. The complete black design is pretty hard on the eye - on my computer and also on my phone. It would be great to introduce/change the current theming to something like: • Light • Dark • Darker Now the main reason why the design is not a good fit (from my point of view): immich is a photo/library app. Of course it is used to backup photos, but I think it is also mainly used to scroll through and view photos. And the scrolling is a problem on (non flagship) smartphones. There is a phenomena called "oled smearing", that will cause the black to smear purple when scrolling. This is pretty hard on the eyes. I propose three solutions here: • Change the current dark theme to a gray background • Introduce a new desi…