IconChanger v1.5.0-pre.2

What's Changed

• feat: switch icons with system appearance
• chore: ignore local design artifacts
• ci: keep appcast publishing idempotent
• ci: deploy Sparkle feed with GitHub Pages
• ci: rebuild Pages after publishing appcast
• ci: allow release workflow to redeploy docs

Full Changelog: v1.5.0-pre.1...v1.5.0-pre.2