feat: add SVG favicon with SL initials and Cornerstone gradient

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

favicon.svg

@@ -0,0 +1,12 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32">
+  <defs>
+    <linearGradient id="g" x1="0%" y1="0%" x2="100%" y2="100%">
+      <stop offset="0%" stop-color="#E31937"/>
+      <stop offset="60%" stop-color="#A82465"/>
+      <stop offset="100%" stop-color="#5236AB"/>
+    </linearGradient>
+  </defs>
+  <rect width="32" height="32" rx="6" fill="url(#g)"/>
+  <text x="16" y="22" font-family="Arial, sans-serif" font-size="14" font-weight="700"
+        fill="#fff" text-anchor="middle" letter-spacing="0">SL</text>
+</svg>

index.html

@@ -9,6 +9,8 @@
   <meta name="description" id="meta-desc" content="">
   <meta name="keywords" id="meta-keywords" content="">
   <link rel="canonical" id="meta-canonical" href="">
+  <link rel="icon" type="image/svg+xml" href="favicon.svg">
+  <link rel="shortcut icon" href="favicon.svg">
   <!-- Open Graph -->
   <meta property="og:type" content="profile">
   <meta property="og:title" id="og-title" content="">