Adds full PWA compliance: web app manifest, service worker with
cache-first static / network-first scoreboard strategy, and a
generated hockey puck icon (512, 192, 180, 32px) on the app's
dark navy background. Includes all required meta tags for iOS
standalone mode and a /favicon.ico route.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
