fix(favicon): add landing-page favicon to fix /favicon.ico 404

Co-Authored-By: Claude Opus 4.7 <[email protected]>

docs/favicon.svg

@@ -0,0 +1,7 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32" width="32" height="32">
+  <rect width="32" height="32" rx="7" fill="#f6821f"/>
+  <g fill="none" stroke="#ffffff" stroke-width="2.2" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M7 9h18c1.1 0 2 .9 2 2v10c0 1.1-.9 2-2 2H7c-1.1 0-2-.9-2-2V11c0-1.1.9-2 2-2z"/>
+    <polyline points="27,11 16,18.5 5,11"/>
+  </g>
+</svg>