Convert App to Multi-Tenant SaaS

The current financial due-diligence application already runs smoothly on Base44 and React; now it needs the infrastructure and polish of a true multi-tenant SaaS. All customer data must be isolated by tenant, with a clean hierarchy of departments and the teams that sit beneath them... (Budget: $10 - $3000 USD, Jobs: API, C# Programming, OAuth, PHP, Ruby on Rails, SaaS, Software Architecture, Stripe)