Run lighthouse for perf stuff, check your headers with [securityheaders.com](http://securityheaders.com), and make sure you're not exposing any server-side env vars to the client. If you used AI for any of the code try npx prodlint, it catches a lot of the stuff AI tends to get wrong like missing rate limiting and exposed error details.
150 hours at 00-150/hr for US market so 5k-22.5k range. Without an admin panel though you're gonna get scope creep fast, the client will want to manage products themselves within a month. I'd factor that in as a follow-up project.
Sshould've linked it. [https://github.com/prodlint/prodlint](https://github.com/prodlint/prodlint) MIT licensed, zero config. Just npx prodlint in any JS/TS project.