One balance row per (user, kind, currency): available and frozen carry the
platform base currency, points carries none. Monetary and points rows use
separate partial unique indexes because a plain UNIQUE lets NULL repeat.
Balance changes go through transactional primitives that debits guard with a
conditional update, credits add atomically, and freeze/release move both sides
in one transaction after locking rows by primary key. Every change appends an
immutable entry holding its resulting balance. Registration and a migration
backfill create the zero rows; GET /api/me/stats is the only public surface and
no endpoint mutates a balance.
The mall buyer center and points page drop the USER_STATS fixture for the
shared contract; the fixture stays exported so the fixed-data adapter can still
serve the account domain as a rollback path.
Implements openspec change add-customer-accounts.
james
7a2745fb16