Technical due diligence code review, small UK SaaS (AI lease reports) - 10-12 hrs + retainer option

I'm acquiring a small B2B SaaS (UK law-firm customers, ~2 years old, two-founder build, hosted on DigitalOcean with a third-party LLM API, PDF in / Word+Excel out). I need a senior full-stack engineer to do a scoped technical review under NDA before close: build and deploy it from the repo, map the architecture and every external service that touches customer data, run a dependency/licence audit, check security basics (auth, RBAC, secrets, encryption, backups), assess the model layer and cost per report, and give me a written risk register with remediation estimates plus a 45-minute call. Fixed scope, 10–12 hours, starting the day repo access is granted (expected within 1–2 weeks). Strong preference for someone who'd take a light on-call retainer afterwards (a few hours/month). Please quote hourly rate or fixed price, availability, and one example of a similar review.