feat: add ThemeToggle component to header login section

apps/frontend/src/components/header.tsx

@@ -195,7 +195,10 @@ export default function Header() {
                     ) : null}
                 </div>
             ) : (
+                <div className="relative flex items-center gap-4" id="menu">
+                    <ThemeToggle />
                     <a href="/api/auth/discord/login" className="text-[16px] text-foreground/50">[ <span className="text-foreground">Login</span> ]</a>
+                </div>
             )}
         </header>
     );