fix: replace all favicon files with Wulf logo

- Replaced favicon.ico with Wulf logo PNG
- Removed old icon.svg (triangle icon)
- Added icon.png with Wulf logo
- All favicon formats now use Wulf logo
- Should fix persistent triangle icon issue

public/icon.svg

@@ -1,10 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32" fill="none">
-  <defs>
-    <linearGradient id="gradient" x1="0%" y1="0%" x2="100%" y2="100%">
-      <stop offset="0%" style="stop-color:#2563eb"/>
-      <stop offset="100%" style="stop-color:#1d4ed8"/>
-    </linearGradient>
-  </defs>
-  <rect width="32" height="32" rx="6" fill="url(#gradient)"/>
-  <path d="M8 16h3l2-6 4 12 3-6h2" stroke="white" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round" fill="none"/>
-</svg>