fix(web): replace PWA icons with full-bleed versions to fix iOS white border

The original icon PNGs had pre-baked rounded corners and transparent
backgrounds. When iOS applies its own superellipse mask on Add to Home
Screen, the transparent corners were filled with white, creating a
visible white border around the icon.

Changes:
- Regenerate all icon PNGs as full-bleed (no rounded corners, opaque
  background filling entire canvas) from the existing logo SVG
- Add dedicated apple-touch-icon.png at 180x180 (iOS standard size)
- Add favicon.ico for universal browser fallback
- Replace oversized app/icon.png (540x540) with 192x192 full-bleed
- Update layout.tsx to reference apple-touch-icon.png
- Add explicit purpose: "any" to 192x192 manifest entry

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/web/app/layout.tsx

@@ -33,7 +33,7 @@ export const metadata: Metadata = {
     title: "Multica",
   },
   icons: {
-    apple: "/logo-192x192.png",
+    apple: "/apple-touch-icon.png",
   },
 };
 

apps/web/app/manifest.ts

@@ -17,6 +17,7 @@ export default function manifest(): MetadataRoute.Manifest {
         src: "/logo-192x192.png",
         sizes: "192x192",
         type: "image/png",
+        purpose: "any",
       },
       {
         src: "/logo-512x512.png",