Payment and admin fulfillment shared the public Redeem entry point, so
fulfillment retries were blocked by, and contributed to, the user's
public redeem failure counter, and lookup errors were silently treated as
"code does not exist" on a partial re-run.
- resolveRedeemAction now distinguishes a genuine not-found lookup from
other lookup errors (which now fail the fulfillment instead of being
swallowed and re-created).
- Add validatePaymentRedeemCode: before reusing an existing code during
fulfillment, verify it belongs to the order (code id, balance type,
amount, user, status), so a stale or foreign code can never be
credited against the wrong order/user.
- Split Redeem into a policy-based core: public redemption enforces the
failure counter; payment fulfillment (redeemForPaymentFulfillment) and
admin fulfillment (RedeemForAdminFulfillment) bypass it, while all code
validation and transactional updates remain identical. Admin
fulfillment keeps the normal redeem-level affiliate rebate.
- The admin CreateAndRedeem endpoint now uses RedeemForAdminFulfillment.
Tests: updated resolveRedeemAction cases, new TestValidatePaymentRedeemCode,
code-used-by-another-user rejection, payment/admin rate-limit bypass
coverage, and public-path regression coverage.