feat(chat): add custom 404 page (#2832)

apps/chat/src/pages/404.tsx

@@ -0,0 +1,35 @@
+import { IconPlus } from '@tabler/icons-react';
+
+import { useTranslation } from '../hooks/useTranslation';
+
+import { Translation } from '../types/translation';
+
+import { getLayout } from './_app';
+
+function Custom404() {
+  const { t } = useTranslation(Translation.Common);
+
+  return (
+    <div className="flex h-screen w-screen flex-col items-center justify-center space-y-4 px-4 text-center">
+      <h1 className="text-6xl font-bold md:text-7xl">{t('404')}</h1>
+
+      <div className="space-y-2">
+        <p className="text-xl font-bold md:text-2xl">{t('Page not found')}</p>
+        <p className="text-base text-secondary">
+          {t("It seems like the page you're looking for doesn't exist.")}
+        </p>
+      </div>
+
+      <a
+        className="button button-secondary flex items-center gap-2 rounded"
+        href={`/`}
+      >
+        <IconPlus size={18} />
+        {t('New Conversation')}
+      </a>
+    </div>
+  );
+}
+
+Custom404.getLayout = getLayout;
+export default Custom404;