Backend (Rust):
- Add position tracking based on elapsed wall clock time
- SharedState now tracks playback start time and position at start
- get_state() returns real-time position instead of stale value
- Position automatically pauses/resumes with playback
Frontend (Svelte):
- Replace dumb setInterval timer with backend polling (500ms)
- Poll get_playback_state to sync position from Rust
- Add onSkipBack/onSkipForward handlers to NowPlayingBar
- Add onSkipBack/onSkipForward handlers to FullScreenNowPlaying
- Wire skip buttons to handlers (restart if >3s, otherwise previous)
- Add keyboard shortcuts: Ctrl+Left/Right for skip