refactor: fix build

[xynydev]

• by fixing the files/ directory migration
• and also updating the files module syntax
• and by copying configurations previously in /usr/etc/ to /etc/

I was looking at this repo for some Pkl inspiration for the examples repo (my conclusion is that it's very convoluted, but eh) and I noticed that the builds were broken, so I did my best to fix them, and apply some of the recent (optional) migrations that make the build process clearer.

I understand you're not actively working on this project right now, but I like the idea, and wanted to try to fix the builds.