Built GearFlow as a multi-sided equipment rental marketplace supporting P2P, platform-owned, and hybrid operating models. I implemented renter/owner roles, listing CRUD, availability and booking conflicts, P2P chat with negotiated offers, rental contracts, escrow/payment workflows, disputes, moderation, reviews, support, analytics, admin controls, Cloudflare R2 uploads, Turnstile, rate limiting, and security hardening. The public repository is a sanitized portfolio build with production credentials excluded.