TASK: Reduce size of login wallpapers

[markusguenther]

Review instructions

Just take a look at the login screen of the backend and decide if the quality is good enogh :)

followup on #5500

[markusguenther]

As the old wallpapers also had 2500px we can save a lot of size here by keeping that.

[mhsdesign]

the images are now in the git either way so changing them again actually increases our repo size.

we were aware of the slightly higher resolution, but jpeg still compressed it smaller than the previous image in smaller dimension.

cc @mficzel

[markusguenther]

I’m a bit confused about the size of the Git repository. The end users don’t really care about it, and it’s already pretty big. The Wallpaper as a JPG is now 493 KB, which is 68% of the previous size. The WebP version is under 400k now.

I know you don’t load the wallpaper often, and hopefully it’s cached, but when your internet connection is slow, it can make a difference.