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-server-installer/files/install.conf

@@ -0,0 +1,20 @@
+# Answers for an unattended Das OS Server installation:
+#   sudo das-server-install --config install.conf
+# The file is read by bash. Every value is checked before anything is done.
+
+# The disk to install to; it is erased completely
+DISK=/dev/vda
+ERASE_DISK=no            # must be "yes" to install
+
+HOST_NAME=dasos-server
+USER_NAME=admin          # gets sudo; root login stays disabled
+USER_PASSWORD=change-me
+
+# A public key for SSH logins (optional), and whether passwords stay allowed
+SSH_KEY=""
+SSH_PASSWORDS=yes        # "no" requires SSH_KEY
+
+TIMEZONE=Europe/Kyiv
+KEYMAP=us                # console layout: us, ua-utf, uk, de-latin1, ...
+LOCALE=en_US.UTF-8       # or uk_UA.UTF-8
+NETWORK=dhcpcd           # or NetworkManager