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/files/fail2ban-das.conf

@@ -0,0 +1,15 @@
+# Das OS: ban addresses that keep failing SSH logins, through nftables.
+[DEFAULT]
+banaction = nftables-multiport
+banaction_allports = nftables-allports
+
+[sshd]
+enabled = true
+backend = polling
+# socklog-void collects auth messages here. svlogd starts each line with a
+# UTC time stamp; the pattern also consumes the facility and the syslog date
+# that follow it, so the sshd filter sees "sshd-session[pid]: ...":
+# 2026-10-19T17:25:46.09500 auth.info: Oct 19 20:25:46 sshd-session[1154]: Invalid user ...
+logpath = /var/log/socklog/secure/current
+datepattern = ^%%Y-%%m-%%dT%%H:%%M:%%S\.%%f(?: \S+: \S+ +\d+ \S+)?
+logtimezone = UTC