fix(docs): remove hero image shadow, move store badges below hero

[o4oren]

Summary

• Removes box-shadow and border-radius from the hero image so it renders cleanly against the FAA background
• Moves App Store / Google Play badges out of the <header> into index.md below the intro text, vertically stacked as originally designed

Changes

• docs/_layouts/home.html — removed store badges div from header
• docs/assets/css/home-custom.css — removed box-shadow and border-radius from .hero-image, removed .store-badges styles
• docs/index.md — added store badges back below intro paragraph, vertically stacked

Test Plan

• Verify hero image has no background box or shadow
• Verify App Store and Google Play badges appear below the intro text, stacked vertically
• Verify badges are not inside the FAA header