I wrote a project to do this a few years ago[1], it's mainly missing an automated mechanism to scan the PDFs and a GUI. Maybe you'll find it interesting.
Since you wrote it in Rust, I'd suggest compiling it to wasm and releasing a browser-based version
That was my eventual plan for having a single GUI for everything, the only problem is that there isn't a really obvious way to support scanning a PDF you upload -- basically you need a pure-Rust PDF renderer and there isn't one up to the task as far as I could tell. On mobile you could scan each QR code separately (though doing this from a webapp is probably going to be a fairly awful UX and most people would prefer to photograph the whole document and get everything scanned automatically).