fix: add missing errors utility and fix seed timestamp casting

- Add apps/api/src/utils/errors.ts with AppError class
- Fix seed.ts timestamp casting for calendario_fiscal

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/web/next-env.d.ts

@@ -0,0 +1,5 @@
+/// <reference types="next" />
+/// <reference types="next/image-types/global" />
+
+// NOTE: This file should not be edited
+// see https://nextjs.org/docs/app/building-your-application/configuring/typescript for more information.