Persist the modular-monolith decision (ADR 0001 handler/service/repo,
ADR 0002 keep REST) with the companion tech spec and the api-architecture
OpenSpec capability. Replace the finished mock-migration tracker with
docs/TBD-marketing.md listing the backend-less marketing domains still on
fixtures (coupons, favorites, account stats, seckill, collective, integral,
reviews). README and AGENTS.md point at the new docs.
Keep the REST contract; move domain logic out of route files so checkout, fulfillment, and identity can be reused across customer, shop, and admin surfaces.
Co-authored-by: Cursor <cursoragent@cursor.com>