Phase 11's "security hardening pass" (docs/10-implementation-roadmap.md), first slice, per explicit user direction. Closes the two concrete gaps 010-identity-auth's own Assumptions named as out of its scope. MFA is intentionally excluded as its own larger follow-up feature. Email delivery for password-reset is stubbed (server-side log) per explicit user decision, since this codebase has no email infrastructure at all today. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>