Arya1230/FileFlex ? reverse-engineered prompt

Build me a simple web app called FileFlex that lets people convert media files online for free. I want users to be able to upload a file, choose the format they want, see the conversion progress, and download the finished file easily. Keep the experience clean and fast, with a modern interface that works well on desktop and mobile.

Make the app feel polished, with clear buttons, helpful messages, and empty states so people always know what to do next. It would be great if the app can support different kinds of media conversions, and if you can include a few common presets people would actually use, even better. Please also make the app ready for multiple languages since I may want to localize it later.

If anything is unclear, use sensible defaults and look up current docs online if you need to.