Blockchain Integration for SaaS Ecommerce

I already have the core SaaS-based ecommerce platform running; what I now need is a solid blockchain layer that plugs in cleanly and scales with the traffic we’re seeing. The focus is squarely on blockchain integration, though the ability to finesse the existing React front-end is a plus.

Here’s what the chain side must cover:
• Smart contracts that automate order life-cycle events—from purchase through fulfilment—written in Solidity (or an equivalent language you can justify).
• On-chain or hybrid payment processing so customers can pay with crypto alongside the current fiat options.
• A secure, decentralised user-authentication flow that plays nicely with OAuth we already use.

I expect gas-efficient, well-commented contracts deployed to a testnet first, full Web3/ethers connectivity in the frontend, and clear hand-over docs for my dev team. Please highlight directly relevant experience—links to live contracts, repos, or production apps speak louder than general CV lines.