Upgrade Next.js to 15.3.3

As we are currently running next v 14.2.25, and the latest stable version is now 15.3.3, it would bring added value to upgrade to the latest version. Of course this is a major release, so care needs to be taken during the upgrade and proper testing Below is a link to the upgrade guide from 14->15 https://nextjs.org/docs/app/guides/upgrading/version-15#upgrading-from-14-to-15