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

apps/web-next/src/app/api/trpc/[trpc]/route.ts

@@ -0,0 +1,12 @@
+import { fetchRequestHandler } from "@trpc/server/adapters/fetch";
+import { appRouter } from "@repo/api";
+
+const handler = (req: Request) =>
+  fetchRequestHandler({
+    endpoint: "/api/trpc",
+    req,
+    router: appRouter,
+    createContext: () => ({}),
+  });
+
+export { handler as GET, handler as POST };