# Implementer — F-020 Shipping module

## Summary
Implemented server-side shipping quotation with zones, methods and free-shipping threshold behind `ShippingService.calculate(cartTotalCents, address)`.

## Files changed
- `project/migrations/015_shipping.js`
- `project/src/modules/shipping/**`
- `project/src/app/build-app.ts`
- `project/src/app/tests/shipping.itest.ts`

## Acceptance evidence
- AC1 known zone: `shipping.itest.ts` seeds ES/28 zone with 500 cents method; `/shipping/calculate` returns 500.
- AC2 unknown zone: same test sends US/94101 and gets HTTP 422 with `SHIPPING_ZONE_NOT_FOUND`.
- AC3 free shipping threshold: same test sends cart total above threshold and gets 0/freeApplied.
- `verify.sh`: passed.

## Commands run
- `cd project && npm run lint/typecheck/build/test` passed
- `cd project && TEST_DATABASE_URL='postgres://mdv:mdv_dev_only@localhost:5432/mdv_test' npm run test:integration -- shipping.itest migrations.itest` passed; 12 files, 47 tests
- `./scripts/verify.sh` passed

## Notes
- No new runtime dependency.
- Carrier adapter remains an interface; no real carrier integration.
- Cheapest active method per zone wins. Postal code prefix matching is most specific first.