Replace Sofa text branding with sofa icon logo

Swap the "Sofa" wordmark for an SVG sofa icon across the nav bar,
auth forms, and landing page. Add SVG favicon replacing the old .ico.

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

components/sofa-logo.tsx

@@ -0,0 +1,28 @@
+export function SofaLogo({
+  size = 24,
+  className,
+}: {
+  size?: number;
+  className?: string;
+}) {
+  return (
+    <svg
+      xmlns="http://www.w3.org/2000/svg"
+      width={size}
+      height={size}
+      viewBox="0 0 24 24"
+      className={className}
+      role="img"
+      aria-label="Sofa"
+    >
+      <path
+        fill="currentColor"
+        d="M7 12v1h10v-1a3 3 0 0 1 2.993-3a4.6 4.6 0 0 0-.07-.78a4 4 0 0 0-3.143-3.143C16.394 5 15.93 5 15 5H9c-.93 0-1.394 0-1.78.077A4 4 0 0 0 4.077 8.22a4.6 4.6 0 0 0-.07.78A3 3 0 0 1 7 12"
+      />
+      <path
+        fill="currentColor"
+        d="M18.444 18H5.556a3.6 3.6 0 0 1-.806-.092V19a.75.75 0 0 1-1.5 0v-1.849A3.55 3.55 0 0 1 2 14.444V12a2 2 0 1 1 4 0v1.2a.8.8 0 0 0 .8.8h10.4a.8.8 0 0 0 .8-.8V12a2 2 0 1 1 4 0v2.444a3.55 3.55 0 0 1-1.25 2.707V19a.75.75 0 0 1-1.5 0v-1.092a3.6 3.6 0 0 1-.806.092"
+      />
+    </svg>
+  );
+}