devdhruvsingh/YouTube-downloader ? reverse-engineered prompt

Build me a simple YouTube downloader web app that lets someone paste a YouTube link, choose a quality or format if that is supported, and download the video or audio to their device.

I want a clean frontend with a straightforward input box, a download button, and clear status messages so people can tell if the link is working, the download is starting, or something went wrong. The backend should handle the actual download logic, expose a small API for the frontend, and be easy to run locally with environment settings from a sample file.

Please keep it polished and easy to use, with sensible error handling for bad links, unavailable videos, and failed downloads. If you need to check current docs or best practices for any library involved, feel free to look them up online. Also make sure the project is organized so it is easy to start, test, and extend later.