- TestPhase8RedRegistration asserts the exact public-client DCR success
contract and fails while Server.Register is a 501 stub
- adds the Backend/Tx transaction-scoped store bundle (ClientStore,
AuthCodeStore, RefreshTokenStore, AccessTokenIssuer) and wristband's own
in-memory implementation for framework-level tests (D-07)
- adds crypto.go's fixed-transform helpers (random base64url, sha256 hex,
constant-time compare, S256) and Options/Server seams for the DCR
lifetimes, cap, sweep age and 64 KiB body bound (D-03/D-21)
