Build an auto repair shop management web app for an independent garage.

1. Customers: name, phone, email, address, notes. A customer can have several vehicles.
2. Vehicles: VIN, year, make, model, trim, plate, current mileage, color, assigned customer. Mileage updates whenever a repair order closes.
3. Repair orders: number, customer, vehicle, complaint, technician, status (checked in, diagnosing, waiting on parts, in progress, ready, picked up), promised date, mileage in.
4. Line items: type (part, labor, sublet, fee), description, quantity, unit price, override flag. Labor lines capture hours and rate. Totals roll up per order.
5. Invoicing: tax per line (parts and labor taxed separately), deposit recorded, payment method (card, cash, check), printable invoice with shop details.
6. Shop floor board: columns by status showing vehicle, customer, technician and promised time, with drag to change status.
7. History: every repair order per vehicle with photos, line items and totals, plus next service due by mileage or date.
8. Reminders: templates for service due, ready for pickup and declined work follow up, sent by email or SMS.
9. Reports: revenue by month, average ticket, margin on parts versus labor, technician productivity.

Rules: never overwrite a line item silently, keep an audit trail of edits on estimates, and make every number editable by the shop.