fix(emqx): increase disk to 6GB and add optional MQ disable prompt

EMQX 6.1+ preallocates significant disk space for the MQ feature,
causing high CPU/disk usage on small containers (emqx/emqx#16649).

- Increase default disk from 4GB to 6GB
- Add read -rp prompt during install to optionally disable MQ feature
  via mq.enable=false in emqx.conf (reduces disk/CPU overhead)
- Setting is in install script (not CT script) per reviewer feedback

Co-authored-by: sim-san <sim-san@users.noreply.github.com>

ct/emqx.sh

@@ -9,7 +9,7 @@ APP="EMQX"
 var_tags="${var_tags:-mqtt}"
 var_cpu="${var_cpu:-2}"
 var_ram="${var_ram:-1024}"
-var_disk="${var_disk:-4}"
+var_disk="${var_disk:-6}"
 var_os="${var_os:-debian}"
 var_version="${var_version:-13}"
 var_unprivileged="${var_unprivileged:-1}"

frontend/public/json/emqx.json

@@ -21,7 +21,7 @@
       "resources": {
         "cpu": 2,
         "ram": 1024,
-        "hdd": 4,
+        "hdd": 6,
         "os": "debian",
         "version": "13"
       }

install/emqx-install.sh

@@ -38,6 +38,18 @@ rm -f "$DEB_FILE"
 echo "$LATEST_VERSION" >~/.emqx
 msg_ok "Installed EMQX"
 
+read -r -p "${TAB3}Would you like to disable the EMQX MQ feature? (reduces disk/CPU usage) <y/N> " prompt
+if [[ ${prompt,,} =~ ^(y|yes)$ ]]; then
+  msg_info "Disabling EMQX MQ feature"
+  mkdir -p /etc/emqx
+  if ! grep -q "^mq.enable" /etc/emqx/emqx.conf 2>/dev/null; then
+    echo "mq.enable = false" >>/etc/emqx/emqx.conf
+  else
+    sed -i 's/^mq.enable.*/mq.enable = false/' /etc/emqx/emqx.conf
+  fi
+  msg_ok "Disabled EMQX MQ feature"
+fi
+
 msg_info "Starting EMQX service"
 $STD systemctl enable -q --now emqx
 msg_ok "Enabled EMQX service"