fix: add pages/_error and _document to fix Html import in build

pages/_error.tsx

@@ -0,0 +1,14 @@
+// Custom error page — prevents Html import issue in Next.js pages router
+export default function Error({ statusCode }: { statusCode?: number }) {
+  return (
+    <div style={{ padding: '2rem', fontFamily: 'sans-serif' }}>
+      <h1>{statusCode || 'Error'}</h1>
+      <p>{statusCode === 404 ? 'Page not found' : 'An error occurred'}</p>
+    </div>
+  );
+}
+
+Error.getInitialProps = ({ res, err }: any) => {
+  const statusCode = res ? res.statusCode : err ? err.statusCode : 404;
+  return { statusCode };
+};