Next.js + Supabase developer to help build our in-house car dealer DMS

We're a busy independent used car dealer in Cardiff, with our own preparation workshop, bodyshop and valeting. A second site is on the way, and I need a developer to keep our in-house system moving while I'm busy with that. WHAT ALREADY EXISTS Over the last six months we've built our own web app, which the whole team uses every day. It covers auction buying, stock and retail pricing, the workshop and parts quotes, bodyshop, garage invoicing, quality checks, transport, weekly sales reviews and a KPI page. Staff sign in with Microsoft 365. - Next.js 15 (App Router), React 19, TypeScript - Supabase: Postgres with row-level security, storage, realtime - Vercel, with a preview deployment for every branch - A separate test copy of the database, so nothing is tried on live data - An always-on automation PC (Python + Playwright) that reads supplier invoices with the Claude API, quotes parts from supplier portals and talks to Xero I'm not a developer by background. Most of the code has been written with Claude Code under my direction, and it is thoroughly documented. WHAT WE NEED BUILT The app is going to replace our current hosted dealer management system (DMS) completely, one area at a time. The target is to be off the old system by the end of 2026. In rough order: 1. Sales and leads: lead-provider emails turned into leads, deals, reservations, handovers, and a diary that pushes bookings into Outlook 2. Customers: one record and one timeline per customer, with email (Microsoft Graph), two-way SMS and WhatsApp (Cloud API) 3. Stock and adverts: AutoTrader Connect API (adverts, reservations, valuations), DVLA/DVSA look-ups, and feeds to other advert sites and our own website 4. Workshop and aftersales: job cards (already started), vehicle inspections, bookings, courtesy cars and technician time cards 5. Accounts: invoices that lock once issued (credit notes, never edits), the VAT margin scheme stock book and VAT return figures, and our vehicle stocking plan with two finance lenders 6. Throughout: an audit trail of who changed what, reports, and support for more than one site Later: a new public website that reads our own stock. WHO I'M LOOKING FOR - Strong Next.js and TypeScript, with real depth in Postgres: schema design, migrations, row-level security, functions and triggers - Experience integrating third-party APIs: OAuth, webhooks, Microsoft Graph, ideally AutoTrader - Comfortable working alongside AI coding tools, and careful about reviewing what they produce - Security-minded: this will hold customer data (UK GDPR) and the company's money records - UK motor trade or DMS experience is a big plus (VAT margin scheme, stock books, vehicle finance) - Explains things in plain English. I make the decisions, so I need the trade-offs in words I can act on - Good overlap with UK working hours HOW WE WORK - Everything is tried on the test copy first. Changes go in by pull request and reach the live app only once I've approved them - The company owns all the code; you'll sign an NDA and an IP assignment - We'll start with a small paid task to see how we work together, with a view to an ongoing role TO APPLY, start your proposal with the word "forecourt" and tell me: - a business system you built on Next.js and Postgres/Supabase that people use every day - any motor trade or DMS work you've done - how many hours a week you can give, and your overlap with UK hours