refactor: use shared get_lxc_ip and get_latest_github_release helpers in addon scripts

- pyenv.sh, webmin.sh, netdata.sh: replace manual hostname -I parsing with get_lxc_ip/$LOCAL_IP
- phpmyadmin.sh: replace manual curl|grep|cut GitHub API version lookup with get_latest_github_release

tools/addon/netdata.sh

@@ -87,7 +87,8 @@ install() {
   $STD apt install -y netdata
   msg_ok "Installed ${APP}"
   msg_ok "Completed successfully!\n"
-  echo -e "\n${APP} should be reachable at${BL} http://$(hostname -I | awk '{print $1}'):19999 ${CL}\n"
+  get_lxc_ip
+  echo -e "\n${APP} should be reachable at${BL} http://${LOCAL_IP}:19999 ${CL}\n"
 }
 
 uninstall() {