Improve offline game experience

[Hugo0]

Current state

webapp/static/offline-game.html is a standalone offline Wordle fallback (185 lines). It loads Tailwind and Vue from CDNs, which defeats the purpose of offline mode — if the user has no connection, the CDN scripts won't load either.

Issues

• CDN dependencies break offline: Loads cdn.tailwindcss.com and unpkg.com/vue@3 — won't work without internet
• Duplicated game logic: Separate implementation from the main frontend/src/game.ts, likely missing features and bug fixes
• No service worker: No PWA service worker to cache the offline page or main game assets
• Limited functionality: Basic grid and keyboard only, no stats, no dark mode toggle, no share button

Suggested improvements

• Bundle offline page with inlined CSS and JS (no CDN deps)
• Add a service worker that caches the main game page + assets for true offline play
• Or: use the Vite build output directly in the service worker cache, so the real game works offline instead of maintaining a separate stripped-down version