refactor: remove theme switching, keep dark mode permanent

src/app/layout.tsx

@@ -48,30 +48,8 @@ export default function RootLayout({
   children: React.ReactNode;
 }>) {
   return (
-    <html lang="en" suppressHydrationWarning={true}>
+    <html lang="en" className="dark" suppressHydrationWarning={true}>
       <head>
-        <script dangerouslySetInnerHTML={{
-          __html: `
-            (function() {
-              const theme = localStorage.getItem('theme-mode') || 'dark';
-              const html = document.documentElement;
-              
-              if (theme === 'dark') {
-                html.classList.add('dark');
-              } else if (theme === 'light') {
-                html.classList.remove('dark');
-              } else if (theme === 'system') {
-                const isDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
-                if (isDark) {
-                  html.classList.add('dark');
-                } else {
-                  html.classList.remove('dark');
-                }
-              }
-            })();
-          `
-        }} />
-      </head>
       <body
         className={`${geistSans.variable} ${geistMono.variable} antialiased`}
       >