feat: Add PWA support for mobile app-like experience

Add manifest.json, meta tags and app icons to enable:
- Add to Home Screen on iOS/Android
- Standalone mode (no browser UI)
- Custom app icon (ROA) and theme color

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

reports-app/frontend/.gitignore

@@ -37,8 +37,9 @@ lerna-debug.log*
 /blob-report/
 /playwright/.cache/
 
-# Test artifacts and debugging files
+# Test artifacts and debugging files (exclude PWA icons)
 *.png
+!public/icon-*.png
 *.jpg
 *.jpeg
 *.webm