feat(ddns-updater): add DDNS-Updater LXC container script

Add bare-metal installation script for qdm12/ddns-updater with web UI
on port 8000, supporting 60+ DNS providers.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

install/ddns-updater-install.sh

@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+
+# Copyright (c) 2021-2026 community-scripts ORG
+# Author: reptil1990
+# License: MIT | https://github.com/community-scripts/ProxmoxVED/raw/main/LICENSE
+# Source: https://github.com/qdm12/ddns-updater
+
+source /dev/stdin <<<"$FUNCTIONS_FILE_PATH"
+color
+verb_ip6
+catch_errors
+setting_up_container
+network_check
+update_os
+
+fetch_and_deploy_gh_release "ddns-updater" "qdm12/ddns-updater" "singlefile" "latest" "/opt/ddns-updater" "ddns-updater_*_linux_amd64"
+
+msg_info "Configuring DDNS-Updater"
+mkdir -p /opt/ddns-updater/data
+cat <<EOF >/opt/ddns-updater/data/config.json
+{
+  "settings": [
+    {
+      "provider": ""
+    }
+  ]
+}
+EOF
+msg_ok "Configured DDNS-Updater"
+
+msg_info "Creating Service"
+cat <<EOF >/etc/systemd/system/ddns-updater.service
+[Unit]
+Description=DDNS-Updater
+After=network.target
+
+[Service]
+Type=simple
+ExecStart=/opt/ddns-updater/ddns-updater
+Environment=DATADIR=/opt/ddns-updater/data
+Environment=LISTENING_ADDRESS=:8000
+Environment=LOG_LEVEL=info
+Environment=PERIOD=5m
+WorkingDirectory=/opt/ddns-updater
+Restart=on-failure
+RestartSec=5
+
+[Install]
+WantedBy=multi-user.target
+EOF
+systemctl enable -q --now ddns-updater
+msg_ok "Created Service"
+
+motd_ssh
+customize
+cleanup_lxc