Fix step icon background

[rajsite]

Pull Request

🤨 Rationale

Fixes two visual issues:

• radial gradients used for the background image of the icon snaps to pixel boundaries and when you have odd scaling (like windows 150% zoom on high res displays) the background doesn't look centered and jitters as it resizes and snaps on pixel boundaries
• border sizes are on pixel boundaries so you see a snapping behavior at the animation end

👩‍💻 Implementation

To address:

• Switched the icon background to a div with a bg color and radius that is transform sized
• Switched the icon border to a box shadow where the sizes can scale continuously

🧪 Testing

Manual tests and chromatic results

✅ Checklist

• I have updated the project documentation to reflect my changes or determined no changes are needed.

[jattasNI]

I verified that both pinch zoom and the Zoom In menu look good on macOS Firefox and Safari