feat: add custom je favicon

SVG icon matching the header logo mark (dark tile, "je", emerald dot),
with a multi-size favicon.ico fallback and an apple-touch-icon.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

components/Layout.js

@@ -16,7 +16,10 @@ export default function Layout({ children, title, description }) {
         <meta property="og:title" content={pageTitle} />
         <meta property="og:description" content={pageDescription} />
         <meta property="og:type" content="website" />
-        <link rel="icon" href="/favicon.ico" />
+        <link rel="icon" href="/favicon.ico" sizes="48x48" />
+        <link rel="icon" href="/icon.svg" type="image/svg+xml" />
+        <link rel="apple-touch-icon" href="/apple-touch-icon.png" />
+        <meta name="theme-color" content="#0c0a09" />
       </Head>
 
       <Header />

public/icon.svg

@@ -0,0 +1,8 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32">
+  <rect width="32" height="32" rx="7" fill="#0c0a09"/>
+  <g fill="none" stroke="#fafaf9" stroke-width="3" stroke-linecap="round">
+    <path d="M11.5 13v9a3.5 3.5 0 0 1-3.5 3.5h-1"/>
+    <path d="M15.5 18h10a5 5 0 1 0-1.46 3.54"/>
+  </g>
+  <circle cx="11.5" cy="8" r="2" fill="#34d399"/>
+</svg>