[Downloads] Smart banners and deep links

[2witstudios]

Summary

Implement smart banners for mobile web and deep link handling.

Technical Details

• iOS Smart App Banner meta tag
• Android app install banner
• Universal links (iOS)
• App links (Android)
• Custom URL scheme fallback

Files

• apps/marketing/src/app/layout.tsx (meta tags)
• apps/marketing/public/.well-known/apple-app-site-association
• apps/marketing/public/.well-known/assetlinks.json

Acceptance Criteria

• Smart banners appear on mobile
• Deep links open app if installed
• Fallback to store if not installed
• Universal/app links configured