Multitenancy solutions - Nextjs - postgre - supabase - vercel

I'm the founder of a Canadian software platform for businesses that rent out workspace: coworking spaces, executive suites (serviced offices with a reception desk), medical and wellness suites (treatment rooms for physios, massage therapists, etc.) and virtual offices. In simple terms, it lets these businesses run everything in one place: • Their locations, floor plans, offices and meeting rooms • Their clients, agreements and monthly invoices (with Canadian GST/HST) • Room bookings, including an online booking page where guests pay by card • Reception: visitors, phone messages and services billed to clients • Mail handling for virtual office clients • A client app where their members book rooms, see invoices and get notices The tech: Next.js 16 on Vercel, Supabase (Postgres), Stripe and Resend. It's multi-tenant, with many companies on one system, and most of the business rules live in Postgres functions and RLS. I'm not a developer myself; I built it with AI tools What I'm looking for: Before I launch, I want an experienced engineer to look at it with fresh eyes and tell me honestly where the risks are, especially: • Keeping each company's (and each client's) data separate • Payments and billing being correct and safe • Anything that could break as more customers join