Stage 4: Calamares installer and Btrfs snapshots (0.2.0)

- Package Calamares 3.4.3 (Qt6, widgets UI) with xbps-src.
- das-installer: Calamares setup for Void/runit with Das OS branding and
  slides. It copies the clean live image (live-base), builds locales and the
  host-only initramfs, rewrites kernels without sparse tails (GRUB 2.12 cannot
  read Btrfs holes at the end of a file), then removes itself.
- das-snapshots: flat Btrfs layout (@, @home, @snapshots, @var_log,
  @var_cache_xbps), snapper with hourly snapshots via cronie, grub-btrfs menu,
  snapper-rollback, and a dracut module that boots read-only snapshots with
  a RAM overlay.
- das-settings 0.2.0: start LightDM with the system locale.
- Live image: GRUB, efibootmgr and the new packages; Das OS /etc/issue.
- Build: wipe stale destdirs before building packages.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

srcpkgs/das-installer/files/installer-icon

@@ -0,0 +1,12 @@
+#!/bin/sh
+# Put the installer launcher on the live user's desktop. Xfce runs launchers
+# from the desktop only when they are executable and marked as trusted.
+desktop=$(xdg-user-dir DESKTOP 2>/dev/null)
+[ -n "$desktop" ] && [ "$desktop" != "$HOME" ] || desktop="$HOME/Desktop"
+launcher="$desktop/das-installer.desktop"
+[ -e "$launcher" ] && exit 0
+
+mkdir -p "$desktop"
+install -m 755 /usr/share/applications/das-installer.desktop "$launcher"
+gio set -t string "$launcher" metadata::xfce-exe-checksum \
+	"$(sha256sum "$launcher" | cut -d' ' -f1)" 2>/dev/null || true