feat(nix): nix and back again

I tried Nix, but it had too many downsides so I removed it.

1. Didn't like that all files are immutable and simple config changes
need a complete rebuild.
2. Setting up a new Mac didn't work as smoothly as promised. Not worth
the effort.
3. It sucked a lot to always have to type in the password twice on each
darwin-rebuild
4. It solves problems I never had.

.config/bat/config

@@ -0,0 +1,8 @@
+--italic-text='always'
+--map-syntax='.*ignore:Git Ignore'
+--map-syntax='.gitconfig.local:Git Config'
+--map-syntax='flake.lock:JSON'
+--pager='less -FR'
+--style='numbers,changes,header,grid'
+--theme='catppuccin-mocha'
+--wrap='never'