fix(alpine-it-tools): write version file after a successful update (#17421)

update_script() compared the upstream tag against /opt/${APP}_version.txt but
never wrote it back, so the stored version stayed at whatever the installer
wrote. Every subsequent run took the update branch, wiping the web root and
re-downloading the full release archive even with no new upstream release.

Write the tag after a successful update, matching what the installer already
does at install/alpine-it-tools-install.sh:42.

Closes #17420

ct/alpine-it-tools.sh

@@ -40,6 +40,7 @@ function update_script() {
     cp -r /tmp/dist/* /usr/share/nginx/html
     rm -rf /tmp/dist
     rm -f it-tools.zip
+    echo "${RELEASE}" >/opt/${APP}_version.txt
     msg_ok "Updated successfully!"
   else
     msg_ok "No update required. ${APP} is already at ${RELEASE}"