windows dark mode/color support + dpi fix + cpp cleanup

[cyn0x8]

semi mirror pr of FunkinCrew/Funkin#4267

• moves window functions into backend.Native
• better dpi awareness (and draws black for a frame so theres no ugly white border)
• added dark theme support toggle function
• added window bar/text/border color functions
• also prunes some of the existing cpp code that is unused

2025-03-08.21-34-43.mp4

[FearmongerWade]

thumbs up

[ShadowMario]

This PR has some problems running on Windows 10 and previous.
If possible, don't make it turn dark mode on by default.

cmd_9g8B5rlHNG.mp4

[ShadowMario]

This PR has some problems running on Windows 10 and previous. If possible, don't make it turn dark mode on by default.

After further thinking, I might reject this PR because of the Dark mode, it's kinda buggy

[cyn0x8]

i can emulate win10 to figure out what might be going on

[DMMaster636]

This PR has some problems running on Windows 10 and previous. If possible, don't make it turn dark mode on by default.

actually, this only happens when doing it in the Main.hx for some reason
in a mod I work on, I made an InitState.hx that handles initializing stuff and having the code there actually fixed the problem
unsure why, but it be like that .>.

[DMMaster636]

tho, an easy way to fix this is to just redraw the header, so for example enabling and disabling borderless
flixel.FlxG.stage.window.borderless = true; flixel.FlxG.stage.window.borderless = false;
it may not be the most optimal solution (because there is a little flash/jitter), but it works

[ShadowMario]

Windows 10 has no native support for changing window colors and stuff, so I'm going to have to close this, the PR will be partially implemented and credited though