mbn217/tools-bin ? reverse-engineered prompt

Build me a clean web app for developers that puts a bunch of handy tools in one place.

I want a modern React frontend with a simple navigation for things like JSON formatting, Base64, URL encoding, JWT decoding, regex testing, markdown preview, CSV and JSON conversion, YAML and JSON conversion, UUID and password generators, QR codes, cron parsing, SQL formatting, HTTP status lookup, invoice generation, and a YouTube transcript tool. Most tools should work right in the browser so they feel fast and private. The transcript tool can use a small backend API.

Make it feel polished and easy to use, with live previews where that makes sense, copy buttons, and clear input and output areas. I’d like it to work nicely on desktop and mobile, and I want route based pages so people can jump straight to any tool. If you need to, look up current docs online for any library choices or deployment details.