Add PWA support for iOS home screen install

- Web app manifest (standalone display, NOMAD branding, icons)
- Service worker with Workbox caching (map tiles, API, uploads, CDN)
- SVG app icon + PNG generation script via sharp
- Apple meta tags (web-app-capable, black-translucent status bar)
- Dynamic theme-color for dark/light mode
- Safe area insets for notch devices

client/package.json

@@ -5,6 +5,7 @@
   "type": "module",
   "scripts": {
     "dev": "vite",
+    "prebuild": "node scripts/generate-icons.mjs",
     "build": "vite build",
     "preview": "vite preview"
   },
@@ -30,7 +31,9 @@
     "@vitejs/plugin-react": "^4.2.1",
     "autoprefixer": "^10.4.18",
     "postcss": "^8.4.35",
+    "sharp": "^0.33.0",
     "tailwindcss": "^3.4.1",
-    "vite": "^5.1.4"
+    "vite": "^5.1.4",
+    "vite-plugin-pwa": "^0.21.0"
   }
 }