Senior Full-Stack SaaS Developer for Existing TypeScript POS System

I own an existing Point of Sale (POS) system built mainly with TypeScript and JavaScript, using a Prisma database. The source code is stored in GitHub, and versions of the system have been deployed on my server. I need an experienced full-stack SaaS developer with a strong understanding of retail POS, inventory, sales, receipts, reporting, and multi-client systems. The first assignment is to audit and secure the GitHub codebase, server, database, backups, and deployment process. The developer must verify that the current GitHub code matches the most recent valid POS updates, create a safe staging/test environment, and document any risks or missing work. I also need the developer to correct existing POS errors, polish the user interface, and add or edit POS functions based on the requirements and visual references I provide. The work must be tested carefully before any live deployment.