feat(header): implement Header component with Logo and UserNav

src/app/(main)/components/header.tsx

@@ -0,0 +1,13 @@
+import { UserNav } from "./user-nav";
+import { Logo } from "@/components/logo";
+
+export default function Header() {
+  return (
+    <div className="h-12 flex items-center">
+      <div className="flex justify-between container mx-auto px-4">
+        <Logo className="h-8 w-auto" />
+        <UserNav />
+      </div>
+    </div>
+  );
+}