Bappaditya-kuilya/Peek ? reverse-engineered prompt

Build me a browser based file sharing app where two devices can send files to each other with no install and no account. One person should pick files on their device, the other should join by scanning a QR code, and the transfer should happen securely with end to end encryption so the server never sees the files or the key. If direct browser to browser transfer works, use that, and if not, fall back to an encrypted relay automatically. I also want the same session to support sending files both ways, plus a simple way to share clipboard text too. It should feel private and temporary, with no saved history, no cookies, and the session should expire on its own after a while or be easy to close immediately. Make it clean and simple to use, and include the ability to share a temporary link for a single file with preview for images and PDFs. If you need to, look up the current docs online for the best way to wire up the browser transfer pieces.