Promote test -> main

[anderdc]

Summary

Promotes 6 commits from test to main:

• 4a3a825 fix(webhook): refresh repo last event on review and comment events (fix(webhook): refresh repo last event on review and comment events #51)
• dd7ee4c feat(dashboard): add slim issues endpoint to replace per-miner fan-out (feat(dashboard): add slim issues endpoint to replace per-miner fan-out #93)
• 8cf0853 fix: fail incomplete pr content fetches (fix: fail incomplete pr content fetches #38)
• 4d8121d fix(mirror): filter cross-repo closing refs (fix(mirror): filter cross-repo closing refs #36)
• 25c37d9 fix: persist transferred issue state (fix: persist transferred issue state #34)
• f5b11c1 Make label_events writes idempotent on backfill ([Bug] Non-idempotent label event insertion duplicates rows on every backfill #25) (Make label_events writes idempotent on backfill (#25) #26)

Prod schema migration (runbook)

packages/db/ is only applied to fresh volumes, so prod needs the following SQL applied manually. Only one change in this batch: the label_events unique index from #26.

The deploy order matters — applying the index against a table that still has duplicates will fail with a unique-violation. That's the intended safety check, not a bug.

1. Merge this PR and let the new code roll out first. orIgnore() in the writer paths is a behavioral no-op until the index exists, so deploying code before the index is safe.

2. Dedupe existing rows. Idempotent; no-op on a clean table. Repeat until 0 rows affected on very large tables:

DELETE FROM label_events a
USING label_events b
WHERE a.id > b.id
  AND a.repo_full_name = b.repo_full_name
  AND a.target_number IS NOT DISTINCT FROM b.target_number
  AND a.target_type    = b.target_type
  AND a.label_name     = b.label_name
  AND a.action         = b.action
  AND a.timestamp      = b.timestamp;

3. Add the unique index CONCURRENTLY so the running app keeps writing during creation. Must run outside a transaction:

CREATE UNIQUE INDEX CONCURRENTLY IF NOT EXISTS uq_label_events_natural_key
    ON label_events (repo_full_name, target_number, target_type,
                     label_name, action, timestamp)
    NULLS NOT DISTINCT;

No other packages/db/*.sql files changed in this batch.

Test plan

• Merge PR and confirm new code is live
• Run the dedupe DELETE against prod; record rows affected
• Run CREATE UNIQUE INDEX CONCURRENTLY ... and verify \d label_events shows uq_label_events_natural_key
• Trigger a backfill on a registered repo and confirm SELECT COUNT(*) FROM label_events is unchanged after the second run