Explicitly whitelist track fields when saving to localStorage to prevent DOM element references (HTMLButtonElement with React fiber) from being serialized. This fixes the circular structure JSON error. Changes: - Changed from spread operator exclusion to explicit field whitelisting - Ensured track.name is always converted to string - Only serialize Track interface fields that should be persisted 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>