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-snapshots/files/dracut/90das-snapshot-overlay/module-setup.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# Dracut module: boot read-only Btrfs snapshots with a writable overlay in RAM.
+
+check() {
+	require_binaries btrfs || return 1
+	return 0
+}
+
+depends() {
+	echo btrfs
+}
+
+installkernel() {
+	hostonly='' instmods overlay
+}
+
+install() {
+	inst_multiple btrfs mktemp
+	inst_hook pre-pivot 10 "$moddir/das-snapshot-overlay.sh"
+}