feat(backend): complete AI and business migration

server/ai/responses.ts

@@ -0,0 +1,12 @@
+import "server-only";
+
+import { NextResponse } from "next/server";
+import { normalizeAiError } from "./provider";
+
+export function aiJsonError(error: unknown): NextResponse {
+  const normalized = normalizeAiError(error);
+  return NextResponse.json(
+    { error: normalized.message, code: normalized.code },
+    { status: normalized.status },
+  );
+}