Backlog: optional email OTP login (deferred due to email volume)

[pataniaeli]

Ticket: AUTH-T100 · Epic: E3 Authentication Core · Phase: Phase 5 — Backlog / spikes
Priority: Low · Estimate: 2 points · Labels: epic:auth-core, phase:5, backlog, email

Depends on:

• Production launch checklist and Primary Admin bootstrap #103 — AUTH-T91 Production launch checklist and Primary Admin bootstrap

Deferred by decision: password is the launch method because Resend free-tier volume is constrained. Revisit after launch: Better Auth emailOTP plugin as an alternative sign-in for users who forget passwords, with strict per-user caps. Requires a volume estimate against the org-wide Resend budget first.

Acceptance criteria

• Decision recorded after reviewing 60 days of email volume metrics.

_{Generated from the SGAuth design (docs/sgauth-design in SGAOperations/auth). SGAuth is built on Neon and does not use Supabase.}