PWA support: manifest + service worker for offline reading

[satsdisco]

Summary

Samizdat is a perfect PWA candidate — writers should be able to draft offline, and readers should be able to read cached articles without connectivity. This is especially important for a freedom press tool (censorship resistance includes network resilience).

Implementation

• Add manifest.json with app name, icons, theme colors, display: standalone
• Service worker for:
  • Cache app shell (HTML, CSS, JS) for offline access
  • Cache read articles for offline reading
  • Queue publish actions when offline, sync when back online
• Use Vite PWA plugin (vite-plugin-pwa) for easy setup
• "Install app" prompt on supported browsers

Acceptance Criteria

• App installable as PWA on Chrome/Safari
• Previously read articles available offline
• Editor works offline (draft saved locally)
• Graceful offline state indicator
• Lighthouse PWA score > 90