v0.4.0: branding refresh, breadpaper baked in, bos-settings 0.4.0

- Move assets to assets/ directory (bread_white.svg, icons 256/512/1024px)
- Update Calamares branding + Plymouth theme logos
- Bake breadpaper (wallpaper manager + pywal) into /etc/skel alongside the
  rest of the bread ecosystem — previously missing from the ISO build
- Bump bos-settings to 0.4.0

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bos-settings"
-version = "0.3.1"
+version = "0.4.0"
 edition = "2021"
 
 [dependencies]