Greetings!
I personally don’t see the need for this. The CubeCraft reports/store/etc website is less of an interactive website, if you get what I’m saying. It’s not a website where you can customize your appearance and such. A website is somewhere you go to do something quickly, there are no settings or controls. And a forum is where you go to interact with the community and stay on the website for a while. Therefore, if you’re only going to be looking at the reports/store/etc website for a short amount of time, there is no need to have a dark mode.
Even if you do feel that it is too bright, you can turn down the brightness, or even invert colors.
Anyways, thanks for the suggestion :)