EchoMusicApp/Echo-Music-Desktop ? reverse-engineered prompt

Build me a desktop music app called Echo Music that feels like a polished YouTube Music client for Windows, Mac, and Linux.

I want it to stream music without ads, let me browse my library and recommendations, and play tracks in high quality. It should also support downloading songs and playlists for offline listening, show synced lyrics while music plays, and translate lyrics into other languages when possible. Please add a sleep timer too, since that’s a nice desktop feature.

Make the app look modern and easy to use, with a good home screen, player view, library view, and settings screen. Use Flutter since this is meant to work across desktop platforms. If you need to check current docs or platform details while building, go ahead and look them up online. Also, please make sure the dark theme looks good, since light mode can be buggy and dark mode should be the default feel.