Commit the generated PNG icons (192/512/maskable + apple-touch) and their
SVG sources so builds work without rsvg-convert: Vite copies public/ into
dist/ as-is, and the Docker build stage cannot regenerate them.
- Add web app manifest, maskable/apple-touch icons, and a production-only
service worker that caches the app shell for offline start
- Improve mobile UX: responsive breakpoints from ~320px, 44px touch
targets, safe-area insets, dvh heights, 16px inputs to avoid iOS zoom
- Serve .webmanifest with correct content type in the Go static handler
- Document PWA behavior and mobile features in the README