perf(api): limit reply failure lookup rows

[thomasorgeval]

Summary

• Use PostgreSQL DISTINCT ON when loading latest publish_failed audit events for Reply Inbox reviews.
• Caps the secondary failure lookup to at most one row per visible review instead of returning every historical publish failure and deduplicating in application code.

Expected impact

• Reduces database result transfer and API-side allocation for Reply Inbox loads when reviews have repeated publish failures.
• The improvement is unmeasured locally because a representative database with high retry/failure volume is needed; behavior should be equivalent because ordering still selects the newest failure per Review.

Verification

• pnpm nx typecheck api --skip-nx-cache
• pnpm lint