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/settings.conf

@@ -0,0 +1,36 @@
+---
+modules-search: [local, /usr/lib/calamares/modules]
+
+sequence:
+  - show:
+    - welcome
+    - locale
+    - keyboard
+    - partition
+    - users
+    - summary
+  - exec:
+    - partition
+    - mount
+    - unpackfs
+    - machineid
+    - fstab
+    - locale
+    - keyboard
+    - localecfg
+    - users
+    - networkcfg
+    - hwclock
+    - packages
+    - bootloader
+    - shellprocess
+    - umount
+  - show:
+    - finished
+
+branding: bos
+prompt-install: true
+dont-chroot: false
+oem-setup: false
+disable-cancel: false
+disable-cancel-during-exec: true