Phase 9: PWA & Workbox Caching

- Added vite-plugin-pwa and workbox-window dependencies
- PWA manifest with icons and standalone display mode
- Workbox runtime caching for:
  - Transformers.js models (30 days)
  - Uploaded images (7 days)
  - Google Fonts (1 year)
- PWAInstall component with install prompt banner
- Offline support for cached assets
- Auto-update registration

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/package.json

@@ -27,6 +27,8 @@
     "eslint-plugin-react-hooks": "^7.1.1",
     "eslint-plugin-react-refresh": "^0.5.2",
     "globals": "^17.5.0",
-    "vite": "^8.0.9"
+    "vite": "^8.0.9",
+    "vite-plugin-pwa": "^0.20.5",
+    "workbox-window": "^7.1.0"
   }
 }