Add favicon matching the site's robot mark and accent color

Adds public/favicon.svg (an SVG favicon, echoing the page's robot
illustration in the --accent blue) and links it from index.html.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

public/favicon.svg

@@ -0,0 +1,9 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64">
+  <rect x="2" y="2" width="60" height="60" rx="16" fill="#2563eb"/>
+  <rect x="10" y="2" width="2" height="10" fill="#ffffff"/>
+  <circle cx="11" cy="2" r="3" fill="#ffffff"/>
+  <circle cx="22" cy="34" r="9" fill="#ffffff"/>
+  <circle cx="22" cy="34" r="3.4" fill="#2563eb"/>
+  <circle cx="42" cy="34" r="9" fill="#ffffff"/>
+  <circle cx="42" cy="34" r="3.4" fill="#2563eb"/>
+</svg>

public/index.html

@@ -4,6 +4,7 @@
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1">
 <title>Ayushya.dev</title>
+<link rel="icon" type="image/svg+xml" href="/favicon.svg">
 <link rel="preconnect" href="https://fonts.googleapis.com">
 <link href="https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@400;500;600;700&display=swap" rel="stylesheet">
 <style>