fix(ui): use app icon in header

Co-Authored-By: Codex <codex@openai.com>

frontend/src/components/Layout.tsx

@@ -3,7 +3,7 @@ import { Link, useLocation, useNavigate } from "react-router-dom";
 import { useAuth } from "../hooks/useAuth";
 import { ThemePreference, useTheme } from "../hooks/useTheme";
 import { api } from "../services/api";
-import { Rocket, Sun, Moon, Monitor } from "lucide-react";
+import { Sun, Moon, Monitor } from "lucide-react";
 
 const themeOptions: { value: ThemePreference; label: string; Icon: typeof Sun }[] = [
   { value: "light", label: "Light", Icon: Sun },
@@ -42,7 +42,7 @@ export function Layout({ children }: { children: React.ReactNode }) {
         <div className="max-w-7xl mx-auto px-4 h-14 flex items-center justify-between gap-4">
           <div className="flex items-center gap-2">
             <Link to="/" className="font-bold text-lg text-blue-600 dark:text-blue-400 hover:opacity-80 inline-flex items-center gap-1.5">
-              <Rocket size={20} /> PR Previews
+              <img src="/icon.png" alt="" className="h-5 w-5 shrink-0 rounded" aria-hidden="true" /> PR Previews
             </Link>
           </div>