Scaffold BOS repo: dotfiles, ISO profile, and bos-settings GTK4 app

Implements all four components from the BOS spec:
- dotfiles/: default Hyprland, bread, breadbox, breadcrumbs configs
- iso/: archiso profiledef, package list, Calamares YAML modules, post-install.sh
- bos-settings/: Cargo workspace with GTK4 settings app (8 views: snapshots,
  packages, bread, breadbar, breadbox, breadcrumbs, breadpad, hyprland)

https://claude.ai/code/session_01WszGHvCmxgcyTwNSkfLF9P

iso/airootfs/etc/calamares/modules/bootloader.conf

@@ -0,0 +1,9 @@
+---
+efiBootloaderId: "BOS"
+installEFIFallback: true
+grubInstall: "grub-install"
+grubMkconfig: "grub-mkconfig"
+grubCfg: "/boot/grub/grub.cfg"
+grubProbe: "grub-probe"
+efiDirectory: "/boot/efi"
+kernel: ""