Stage 6: server image with a console installer (0.4.0)

- server/ profile and build-iso.sh [desktop|server]; make iso-server,
  make qemu-server, run-qemu.sh --serial; login on tty and ttyS0
- das-server: SSH, chrony, NetworkManager/dhcpcd, Docker with Compose,
  nftables (closed except SSH, own table), fail2ban reading socklog,
  sshd without root passwords, Docker log rotation, tools
- das-server-install: dialog installer in Ukrainian and English, or
  unattended with --config; GPT + Btrfs subvolumes, GRUB for UEFI and BIOS,
  serial console, SSH key with optional keys-only logins
- das-install-common: mount-source and postinstall shared with Calamares
- dsv: runit service manager (list, enable, disable, start, stop,
  restart, status, logs) with bash completion, also on the desktop
- das-update split into a subpackage without GTK; the window and tray
  icon move to /usr/libexec/das/das-update-gui
- das-snapper-setup enables dbus, which snapper needs
- TODO: ISO size review with measured numbers and options

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

srcpkgs/das-install-common/files/mount-source

@@ -0,0 +1,17 @@
+#!/bin/sh
+# Mount the clean live image for Calamares' unpackfs at /run/das-installer/root.
+#
+# Dracut runs the live root as a device-mapper snapshot (live-rw) that also
+# holds the live user and boot-time tweaks. Its origin, live-base, is the
+# untouched LiveOS/rootfs.img; mount it read-only without journal replay.
+set -eu
+
+root=/run/das-installer/root
+mountpoint -q "$root" && exit 0
+
+if [ ! -b /dev/mapper/live-base ]; then
+	echo "mount-source: /dev/mapper/live-base not found, is this the live system?" >&2
+	exit 1
+fi
+mkdir -p "$root"
+mount -o ro,noload /dev/mapper/live-base "$root"