fix(site): reference the app icon png directly

The svg icon is only a wrapper around app-icon.png, and the nested
reference is invisible to the static copy step, so the image stayed
invisible on production even after the svg itself deployed.

site/index.html

@@ -10,7 +10,7 @@
     >
     <link rel="preconnect" href="https://fonts.googleapis.com">
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
-    <link rel="icon" href="/images/app-icon.svg" type="image/svg+xml">
+    <link rel="icon" href="/images/app-icon.png" type="image/png">
     <meta property="og:type" content="website">
     <meta property="og:title" content="Claude Code Haha — Claude Code 的桌面工作室">
     <meta

site/src/components/DocPage.jsx

@@ -147,7 +147,7 @@ export function DocPage({
             onNavigate(homeRoute)
           }}
         >
-          <img src={toSiteHref('/images/app-icon.svg')} alt="" />
+          <img src={toSiteHref('/images/app-icon.png')} alt="" />
           <span>Claude Code Haha</span>
           <small>Docs</small>
         </a>