refactor(mqttx): convert from LXC to addon

MQTTX Web is a static browser-based MQTT client with no backend.
Makes more sense as an addon installable into any existing container
than as a dedicated LXC.

Addon installs into /opt/mqttx, builds web/ with yarn, serves via
Nginx on configurable port (default 8095). Supports install/update/uninstall.

tools/addon/mqttx.sh

@@ -0,0 +1,136 @@
+#!/usr/bin/env bash
+
+# community-scripts ORG | MQTTX Web Addon Installer
+# Author: MickLesk
+# License: MIT
+# Source: https://github.com/emqx/MQTTX
+
+if command -v curl >/dev/null 2>&1; then
+  source <(curl -fsSL https://git.community-scripts.org/community-scripts/ProxmoxVED/raw/branch/main/misc/core.func)
+  load_functions
+elif command -v wget >/dev/null 2>&1; then
+  source <(wget -qO- https://git.community-scripts.org/community-scripts/ProxmoxVED/raw/branch/main/misc/core.func)
+  load_functions
+fi
+source <(curl -fsSL https://git.community-scripts.org/community-scripts/ProxmoxVED/raw/branch/main/misc/tools.func)
+
+color
+catch_errors
+
+APP="MQTTX Web"
+APP_TYPE="tools"
+APP_DIR="/opt/mqttx"
+SERVICE="mqttx-web"
+REPO="emqx/MQTTX"
+DEFAULT_PORT=8095
+
+header_info "$APP"
+
+if ! grep -q -Ei 'debian|ubuntu' /etc/os-release; then
+  msg_error "Unsupported OS. This addon supports only Debian or Ubuntu."
+  exit 1
+fi
+
+IP=$(hostname -I | awk '{print $1}')
+
+function is_installed() {
+  [[ -d "$APP_DIR/web/dist" ]] && systemctl is-active --quiet "$SERVICE"
+}
+
+function install_mqttx() {
+  local port="${1:-$DEFAULT_PORT}"
+
+  NODE_VERSION="22" NODE_MODULE="yarn" setup_nodejs
+
+  fetch_and_deploy_gh_release "mqttx" "$REPO" "tarball" "latest" "$APP_DIR"
+
+  msg_info "Building ${APP}"
+  cd "$APP_DIR/web"
+  $STD yarn install --frozen-lockfile
+  $STD yarn build
+  msg_ok "Built ${APP}"
+
+  if ! dpkg -l nginx &>/dev/null; then
+    msg_info "Installing Nginx"
+    $STD apt install -y nginx
+    msg_ok "Installed Nginx"
+  fi
+
+  msg_info "Configuring ${APP}"
+  cat <<EOF >/etc/nginx/sites-available/mqttx-web
+server {
+    listen ${port};
+
+    root ${APP_DIR}/web/dist;
+    index index.html;
+
+    location / {
+        try_files \$uri \$uri/ /index.html;
+    }
+}
+EOF
+  ln -sf /etc/nginx/sites-available/mqttx-web /etc/nginx/sites-enabled/mqttx-web
+  $STD nginx -t
+  systemctl reload nginx
+
+  cat <<EOF >/etc/systemd/system/${SERVICE}.service
+[Unit]
+Description=${APP} (Nginx on port ${port})
+After=network.target
+BindsTo=nginx.service
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/bin/true
+ExecReload=/usr/sbin/nginx -s reload
+
+[Install]
+WantedBy=multi-user.target
+EOF
+  systemctl enable -q --now "$SERVICE"
+  msg_ok "${APP} installed at http://${IP}:${port}"
+}
+
+function uninstall_mqttx() {
+  msg_info "Removing ${APP}"
+  systemctl disable -q --now "$SERVICE" 2>/dev/null || true
+  rm -f "/etc/systemd/system/${SERVICE}.service"
+  rm -f /etc/nginx/sites-enabled/mqttx-web
+  rm -f /etc/nginx/sites-available/mqttx-web
+  $STD nginx -t && systemctl reload nginx
+  rm -rf "$APP_DIR"
+  msg_ok "${APP} uninstalled"
+}
+
+function update_mqttx() {
+  if check_for_gh_release "mqttx" "$REPO"; then
+    msg_info "Updating ${APP}"
+    CLEAN_INSTALL=1 fetch_and_deploy_gh_release "mqttx" "$REPO" "tarball" "latest" "$APP_DIR"
+    cd "$APP_DIR/web"
+    $STD yarn install --frozen-lockfile
+    $STD yarn build
+    systemctl reload nginx
+    msg_ok "${APP} updated"
+  else
+    msg_ok "${APP} is already up-to-date"
+  fi
+}
+
+if is_installed; then
+  read -r -p "Update (1), Uninstall (2), Cancel (3)? [1/2/3]: " action
+  action="${action//[[:space:]]/}"
+  case "$action" in
+  1) update_mqttx ;;
+  2) uninstall_mqttx ;;
+  3) msg_info "Cancelled" ;;
+  *) msg_error "Invalid input" ;;
+  esac
+else
+  echo -e "${TAB}Enter port number (default: ${DEFAULT_PORT}): "
+  read -r PORT_INPUT
+  PORT="${PORT_INPUT:-$DEFAULT_PORT}"
+  read -r -p "Install ${APP}? (y/n): " answer
+  answer="${answer//[[:space:]]/}"
+  [[ "${answer,,}" =~ ^(y|yes)$ ]] && install_mqttx "$PORT" || msg_info "Installation skipped"
+fi