feat(loading): preload portfolio assets before reveal

src/app/layout.tsx

@@ -16,6 +16,7 @@ export const metadata: Metadata = {
 };
 
 const themeScript = `
+  document.documentElement.dataset.siteLoading = 'true';
   try {
     const savedTheme = localStorage.getItem('portfolio-theme');
     const systemTheme = matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
@@ -35,6 +36,9 @@ export default function RootLayout({
       </head>
       <body>
         <ThemeProvider>{children}</ThemeProvider>
+        <noscript>
+          <style>{`#site-loader { display: none !important; }`}</style>
+        </noscript>
       </body>
     </html>
   );