Fix step marker background visibility issue

Summary

the before: elements in @frontend/components/HomeOnboardingWizard.tsx stepmarkers don't have a solid background (I can see the dotted after borders through the background)

Edited

Adjusted the step marker layering so the before: circle sits above the dotted after line and blocks it. This keeps the background solid without the dashed line bleeding through.

Changed in frontend/components/HomeOnboardingWizard.tsx.

If you want, I can run bun run lint to confirm no class issues.