Add PWA support to all static HTML apps

[corvid-agent]

Summary

None of the 12 static HTML apps have PWA support. Many would benefit from offline use and home screen installability.

Repos needing PWA

• algo-explorer
• pd-radio
• corvid-agent.github.io
• corvidlabs-landing
• nft-gallery
• code-playground
• typing-test
• morse-code
• markdown-wiki
• agent-profile
• agent-dashboard
• world-clock
• apps

What each needs

• manifest.json with app name, icons, theme color, display: standalone
• Basic service worker for offline shell caching
• Cache strategy appropriate to the app (cache-first for static, network-first for API data)
• <link rel="manifest"> in index.html

Note

Some Angular apps already have PWA via @angular/pwa (bw-cinema, pd-gallery, pd-audiobooks, pd-music, weather-dashboard, retro-arcade). The remaining Angular apps without PWA are tracked in #3.