AR Web App

We need to rebuild an AR app that plays animations when a user moves their phone camera over a flat target (this would likely be a large painting on a wall IRL - but could also be a postcard or sticker) At the moment we have an iOS app and Android (search for "Gif-iti" in the app stores) - but ideally we'd like to handle everything in a phone browser so we only need one production build. We have done some tests using A-Frame VR but the quality is not great. Perhaps using Unity (or similar) would be an option? Feel free to recommend other suitable technologies! We have dozens of existing targets and animations (either mp4s or GIFs) - each target/animation can have it's own URL. We can use QR codes next to the paintings to link users to the correct mobile web page. We would need the ability to upload our own targets/videos. We need this fully functional by the end of May. Thanks!