mohammednihadv/euphony ? reverse-engineered prompt

Build me a modern music player app called Euphony that works on Android, Windows, macOS, and Linux.

I want it to feel fast, clean, and completely ad free, with a bold high contrast look that works in both light and dark mode, plus a true black theme for OLED screens. It should let users search their music by track, album, artist, or playlist, play local files offline, and manage a queue with shuffle, repeat all, and repeat one. Add playback speed controls from 0.75x to 2x, a sleep timer that fades out nicely, and native media controls for the lock screen and notifications. The app should also support playlists saved locally, offline downloads, adaptive audio quality, and simple backup and restore for playlists and downloads.

Make it polished and ready to run on desktop and mobile, and if you need to check current Flutter or platform docs, look them up online.