feat: light theme by default with dark toggle, CSS variables, FOUC prevention, theme persistence

app/login/page.js

@@ -2,6 +2,7 @@
 import { useState } from 'react';
 import { useRouter } from 'next/navigation';
 import { Sparkles } from 'lucide-react';
+import ThemeToggle from '@/components/ThemeToggle';
 
 export default function LoginPage() {
   const router = useRouter();
@@ -30,7 +31,10 @@ export default function LoginPage() {
   }
 
   return (
-    <main className="min-h-screen flex items-center justify-center p-4">
+    <main className="min-h-screen flex items-center justify-center p-4 relative">
+      <div className="absolute top-4 right-4">
+        <ThemeToggle />
+      </div>
       <div className="w-full max-w-md">
         <div className="flex items-center gap-2 mb-8 justify-center">
           <Sparkles className="w-7 h-7 text-accent" />