iso: add bos-rescue, first-boot probe, optional Calamares refresh

Live-ISO bos-rescue finds the installed btrfs @ and ESP, then offers
arch-chroot and/or the same GRUB NVRAM + --removable sequence as
post-install.sh. Recovery is grub-btrfs or this reinstall — GRUB pins
rootflags=subvol=@.

bos-first-boot runs once after the first graphical login: NVIDIA offer
file + notify (no driver install), VM-without-GL notify, HiDPI hint
file (never rewrites monitors.json).

Re-enable the Calamares packages module as a refresh-only step with
skip_if_no_internet and ignore_update_db_error so offline installs
cannot abort on pacman -Sy.

iso/airootfs/etc/skel/.config/hypr/hyprland.lua

@@ -174,6 +174,7 @@ hl.on("hyprland.start", function()
             "breadbar",
             "hypridle",
             "bos-netcheck",
+            "bash -c 'command -v bos-first-boot >/dev/null && exec bos-first-boot'",
             "breadhelp --autostart",
             "bash -c 'command -v breadpaper >/dev/null && exec breadpaper listen'",
             "bash -c 'command -v breadshot >/dev/null && exec breadshot listen'",