Sparkle v0.4.0

What's Changed

• fix: lead synced lyric transitions into timestamps by @doabell in #14
• fix: stabilize lyrics and player transitions by @doabell in #15
• feat: add now-playing layouts and unify app appearance by @doabell in #16
• test: add TypeScript and Rust coverage gates by @doabell in #17

Full Changelog: v0.3.0...v0.4.0