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.

ct/mqttx.sh

@@ -1,60 +0,0 @@
-#!/usr/bin/env bash
-source <(curl -fsSL https://raw.githubusercontent.com/community-scripts/ProxmoxVED/main/misc/build.func)
-
-# Copyright (c) 2021-2026 community-scripts ORG
-# Author: MickLesk (CanbiZ)
-# License: MIT | https://github.com/community-scripts/ProxmoxVED/raw/main/LICENSE
-# Source: https://github.com/emqx/MQTTX
-
-APP="MQTTX Web"
-var_tags="${var_tags:-mqtt;iot;messaging}"
-var_cpu="${var_cpu:-1}"
-var_ram="${var_ram:-1024}"
-var_disk="${var_disk:-4}"
-var_os="${var_os:-debian}"
-var_version="${var_version:-13}"
-var_unprivileged="${var_unprivileged:-1}"
-
-header_info "$APP"
-variables
-color
-catch_errors
-
-function update_script() {
-  header_info
-  check_container_storage
-  check_container_resources
-
-  if [[ ! -d /opt/mqttx ]]; then
-    msg_error "No ${APP} Installation Found!"
-    exit
-  fi
-
-  if check_for_gh_release "mqttx" "emqx/MQTTX"; then
-    msg_info "Stopping Nginx"
-    systemctl stop nginx
-    msg_ok "Stopped Nginx"
-
-    msg_info "Updating MQTTX Web"
-    fetch_and_deploy_gh_release "mqttx" "emqx/MQTTX" "tarball" "latest" "/opt/mqttx"
-    cd /opt/mqttx/web
-    $STD yarn install --frozen-lockfile
-    $STD yarn build
-    msg_ok "Updated MQTTX Web"
-
-    msg_info "Starting Nginx"
-    systemctl start nginx
-    msg_ok "Started Nginx"
-    msg_ok "Updated successfully!"
-  fi
-  exit
-}
-
-start
-build_container
-description
-
-msg_ok "Completed Successfully!\n"
-echo -e "${CREATING}${GN}${APP} setup has been successfully initialized!${CL}"
-echo -e "${INFO}${YW} Access it using the following URL:${CL}"
-echo -e "${TAB}${GATEWAY}${BGN}http://${IP}:80${CL}"