Add PWA support and mobile optimizations

- Add manifest.json with PWA configuration
- Add viewport settings for iOS (viewport-fit: cover)
- Add meta tags for iOS Safari (apple-mobile-web-app-capable)
- Add mobile CSS optimizations:
  * iOS Safe Area support
  * Minimum 44x44px touch targets
  * Disable zoom on input focus
  * Remove scrollbars on mobile
  * Disable hover effects on touch devices
  * Standalone mode styles
- Add InstallPrompt component for Add to Home Screen
- Add SVG icon (needs PNG conversion)

frontend/public/icon-192.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="192" height="192" viewBox="0 0 192 192">
+  <rect width="192" height="192" rx="24" fill="#1B1A55"/>
+  <text x="96" y="100" font-family="Arial, sans-serif" font-size="80" font-weight="bold" fill="#9290C3" text-anchor="middle">W</text>
+</svg>