v1.5.0: harden private context and verified email delivery

[Alex0158]

Summary

• hard-off private-derived controls in shared/formal mediation until per-owner compiler and consent exist; keep formal shared output on evidence-only Decision Core
• revalidate AI stream participant and exact-scope entitlement for every payload
• replace plaintext OTP flow with HMAC challenges, provider-accepted delivery, one-time registration proof, verified-user creation, legacy unverified-account recovery, and CITEXT email safety
• redesign Web/App registration around the same server-timed proof-first flow and add accessible recovery UI
• fail closed on Production SMTP startup/readiness, redact email/OTP/proof/JWT logs, add authenticated TLS CI sink and mandatory provider canary evidence

Verification

• Backend: build + lint; 200 passed suites / 2470 passed tests (2 suites and 39 tests skipped)
• Web: build + lint; 179 files / 2018 tests
• Admin: build + lint; 16 files / 52 tests
• App: typecheck and contract checks; 36 suites / 214 tests
• API client: 6 suites / 40 tests
• migration/release/redaction focused: 7 suites / 71 tests
• email release contract: 9 / 9
• backend npm audit: 0 critical/high/moderate; 1 low transitive dev-tool advisory
• GitHub CI: 7 / 7 passed on run 29260520865
• docs:check and docs:audit:dry-run:current passed
• fresh PostgreSQL migrations, CITEXT compatibility, production-like true-service registration/claim smoke, and browser registration flow passed locally

Production stop condition

Do not merge or deploy until Railway Production has all required values: EMAIL_DELIVERY_MODE=smtp, EMAIL_FROM, EMAIL_OTP_PEPPER, SMTP_HOST, SMTP_PORT, SMTP_USER, SMTP_PASS, SMTP_SECURE or SMTP_REQUIRE_TLS, and EMAIL_CANARY_RECIPIENT. The new backend intentionally fails startup/readiness without them.

The provider canary runs on the GitHub runner using Production Railway variables. Combined evidence proves exact deployed startup readiness plus provider acceptance using the same Production configuration; it does not prove the exact deployed process sent the message or that the inbox received it.

Residual boundaries

• deployment intentionally invalidates legacy plaintext OTPs; users with a code issued in the previous five minutes must resend
• password reset response is content/status neutral, but synchronous provider timing remains a documented P2 side channel until a durable outbox exists
• per-owner Strategy Compiler, adaptation consent, Safety Router, cross-case memory, live two-party and native-device evidence remain tracked work; this PR is containment, not full private-memory completion

[Alex0158]

Superseded by consolidated PR #12, which includes this complete change set plus the private-context and Safety P0 slice and has exact-head CI 7 of 7 green. The Production SMTP stop condition is unchanged, so #12 remains Draft and unmerged.