feat: durable delivery stages and follow-up snapshots (package 2)

[nikolajIvanov]

Package 2: durable delivery reliability (dependent draft)

Depends on creator workflow #85. This branch includes that prerequisite commit, so the upstream diff is cumulative. The delivery-only review is the package commit or the package-only comparison.
Please review/merge #85 first; this draft can then be rebased to a small standalone diff. Do not merge prerequisite changes twice.

Changes

• Additive DeliveryEvent migration, durable stage claims and a workspace-scoped, sanitized delivery history.
• Freeze trigger selection and follow-up content/version. Recover missing Redis enqueue operations from PostgreSQL.
• Verify actual interaction timestamps, the 24-hour window, account connection and recipient identity before follow-ups.
• Keep successful or ambiguous claims from being automatically resent. Confirmed postback retries record their current message and campaign version consistently.
• Native PostgreSQL upserts fix concurrency races reproduced by parallel real-database tests; persistence failures release reserved quota.

Verification

• 390 tests / 35 files passed with real PostgreSQL, including repeated concurrency probes.
• Full TypeScript, targeted ESLint, diff checks and an actual production build passed with the exact upstream lockfile.
• Independent review found and retested the race and postback-version fixes. Changed files were reviewed for private data.
• No real Meta send or production deployment was performed.

Operational boundaries

Apply migrations before starting the new web and worker versions. Review docs/delivery-retries.md before release.
Ambiguous/crashed claims deliberately require manual reconciliation; this is not an exactly-once network delivery guarantee.
Zernio currently does not forward a verified interaction timestamp in normalization, so follow-ups fail closed as SKIPPED on that path.
This package naturally resolves the existing nullable operationId type error in the modified worker flow; it does not silently alter unrelated code.
No ServiceKey/MCP/conversion functionality, auth/SMTP changes, Docker changes or dependency changes are included in the delivery-only commit. Existing upstream dependency audit findings remain outside this package.

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