Tracks HMAC-failure count separately from consecutive_failures (network
errors). Auth failures and network failures have different resolution
paths; mixing them would let a single successful retry after a network
blip mask real secret desync.
Part of backlog #19 — outbox auth-failure recovery.
Note: drizzle-kit generated the 0003 SQL with an unexpected CREATE TABLE
for peer_approval_requests because the 0002 migration was authored
manually without a corresponding 0002_snapshot.json (see 14041e9). The
generated SQL has been trimmed to the single intended ALTER TABLE. The
regenerated 0003_snapshot.json correctly reflects the full current
schema, so future migrations will diff cleanly.
