Pure-logic module: generate 8-digit codes, Argon2id PHC hash with OS RNG salt, verify via constant-time PasswordVerifier. Dead-code allow until Task 4 wires the store on top. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Pure-logic module: generate 8-digit codes, Argon2id PHC hash with OS RNG salt, verify via constant-time PasswordVerifier. Dead-code allow until Task 4 wires the store on top. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>