feat(pwa): add Serwist service worker, manifest, icons, install prompt
- Wrap next.config.ts with @serwist/next (webpack mode, disabled in dev)
- Service worker: NetworkOnly for /api/*, offline fallback → /~offline
- Web app manifest via Next.js metadata API (app/manifest.ts)
- PNG icon set generated with sharp (192, 512, maskable-512, apple-180)
- iOS meta tags: appleWebApp, themeColor viewport export
- Middleware: pwaAssets early-return so /sw.js never gets a 302→login
- Offline fallback page at /~offline (static, no auth dependency)
- InstallPrompt component: beforeinstallprompt (Android) + iOS Share sheet instructions
- Logout (menu/page.tsx): purge all SW caches on signout (shared-device safety)
- Fix invite/[token]/page.tsx params type for Next.js 16 (use(params))
- Build script: next build --webpack (Serwist requires webpack, not Turbopack)
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Mannu
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