feat: improve structure and error handling

app/[lang]/(preview)/not-found.tsx

@@ -1,7 +1,7 @@
 export default function NotFound() {
   return (
     <main>
-      <h2>Not Found</h2>
+      <h1>Not found</h1>
       <p>Could not find requested resource</p>
     </main>
   )

app/[lang]/(preview)/preview/[contentType]/[uid]/page.tsx

@@ -0,0 +1,20 @@
+import {
+  ContentTypeParams,
+  LangParams,
+  PageArgs,
+  UIDParams,
+} from "@/types/params"
+
+export default async function PreviewPage({
+  params,
+  searchParams,
+}: PageArgs<LangParams & ContentTypeParams & UIDParams, {}>) {
+  return (
+    <div>
+      <p>
+        Preview for {params.contentType}:{params.uid} in {params.lang} with
+        params <pre>{JSON.stringify(searchParams, null, 2)}</pre> goes here
+      </p>
+    </div>
+  )
+}

app/[lang]/(preview)/preview/page.tsx

@@ -1,3 +0,0 @@
-export default async function PreviewPage() {
-  return null
-}