- Add web app manifest with proper metadata and icon support
- Configure vite-plugin-pwa with injectManifest strategy
- Migrate service worker to Workbox with precaching and runtime caching
- Add runtime caching for cross-origin images (preserves existing behavior)
- Add runtime caching for cross-origin article HTML for offline reading
- Create PWA install hook and UI component in settings
- Add online/offline status monitoring and toast notifications
- Add service worker update notifications
- Add placeholder PWA icons (192x192, 512x512, maskable variants)
- Update HTML with manifest link and theme-color meta tag
- Preserve existing relay/airplane mode functionality (WebSockets not intercepted)
The app now passes PWA installability criteria while maintaining all existing
offline functionality. Icons should be replaced with proper branded designs.
