feat(web-next): add Next.js 15 app shell with tRPC endpoint

apps/web-next/src/app/page.tsx

@@ -0,0 +1,8 @@
+export default function Home() {
+  return (
+    <main>
+      <h1>Template — Next.js</h1>
+      <p>Clean Architecture Monorepo Template</p>
+    </main>
+  );
+}