The PG implementation was a single UPDATE ... WHERE code_hash that returned
ErrNotFound on zero rows: every wrong, expired, replayed or superseded code on
the pre-session email-login door (and the op-login finish / migration confirm
doors) fell through to writeError's unmapped-error 500, and attempts were never
charged so otpMaxAttempts/ErrOTPLocked could not trigger. The fake repo and the
Repo interface ("SAME code lifecycle as VerifyEmailOTP") already documented the
intended contract; only the PG side had drifted.
Mirror VerifyEmailOTP's transaction without its users write: SELECT ... FOR
UPDATE the newest live row, expiry + attempt cap before the hash compare,
mismatch charges one attempt and returns ErrOTPInvalid without consuming,
match consumes and commits. Verified live on the VM: 5 wrong guesses return
400 and stop at attempts=5 (correct code then also refused, unconsumed);
fresh code redeems; replay returns 400.
Lemon-miaow
52549f7b3a