#8331 improvement(db): tag advisory lock statements by caller

Summary

• Every transaction-scoped advisory lock in apps/sim ran the same statement, SELECT pg_advisory_xact_lock(hashtextextended($1, 0)), so query insights showed all lock waits as one fingerprint with no way to tell which caller was waiting
• New acquireAdvisoryXactLock(tx, tag, key) and tryAcquireAdvisoryXactLock(tx, tag, key) in lib/db/advisory-locks.ts issue the same call with a trailing SQLCommenter tag (/*lock='<family>'*/), which PlanetScale query tags can filter on. The tag must be a static snake_case identifier, so it can't break out of the comment
• About 45 call sites now go through the helper, each tagged with its lock family (user_table_rows_pos, organization_membership, usage_log_event, …). Keys, lock types, timeouts, and transaction boundaries are unchanged
• Left alone: statements whose SQL text is already unique (packages/db locks, the file-search dispatch generate_series claim) and one untyped repair script

Type of Change

• Improvement

Testing

• New lib/db/advisory-locks.integration.ts (real Postgres):
  • the same key blocks and releases on commit; a different key doesn't block
  • the try variant returns false while held
  • the tag reaches the server (checked through pg_stat_activity)
  • an unsafe tag is rejected
• Each test goes red when its guarantee is broken
• Type-check, lint, check:audits, and unit tests for every changed file pass

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)