- Introduce a full-screen "Now Playing" overlay modal with left (cover/creator) and right (track list/controls) panels
- Add CSS styles for animated cyan-themed overlay, track list, progress bar, and equalizer visualizer
- Integrate new `now-playing.js` module and update layout to include it
- Refactor playlist action buttons to include a "Now Playing" reopen button that appears when playback starts
- Dispatch `briTunes:queue` event on queue initialization for external UI synchronization
