Create favicon from logo

- Replaced favicon icon with simplified Q logo (public/favicon.png)
- Updated HTML to reference new PNG favicon in index.html (link rel="icon")

X-Lovable-Edit-ID: edt-90147a21-561a-4e2f-9e56-3c7d89d4517c

index.html

@@ -16,7 +16,7 @@
     <meta name="apple-mobile-web-app-title" content="Ore Cart" />
     
     <!-- PWA Icons -->
-    <link rel="icon" href="/favicon.ico" />
+    <link rel="icon" href="/favicon.png" type="image/png" />
     <link rel="apple-touch-icon" href="/apple-touch-icon.png" />
     
     <!-- Open Graph -->