rafatosta/zapzap — reverse-engineered prompt

Build me an unofficial WhatsApp desktop app for Linux and Windows that feels much closer to a native app, but it should really just wrap WhatsApp Web since there is no public API. I want a polished desktop experience with light and dark mode, fullscreen, keyboard shortcuts, tray icon notifications, background running, drag and drop, adjustable interface scaling for high resolution screens, and support for switching between multiple accounts in a simple grid view.

Please include a proper settings area where people can pick download folders, use a temporary folder for opening files, choose spellcheck languages, and tweak performance and tray icon behavior. I also want a customization section where users can add their own CSS and JavaScript globally or per account, import files or https URLs, enable or disable them, edit them in the app, and reload the page after saving.

Make file uploads, opening PDFs, and drag and drop work as well as possible on Linux, and explain any folder permission needs clearly for sandboxed installs. If you need to, look up current docs online.