I-003: job timeout reaper closes AwaitingCSR/AwaitingApproval gap

Add 11th always-on scheduler loop that transitions jobs stuck in
AwaitingCSR (default 24h TTL) or AwaitingApproval (default 168h TTL)
to Failed. I-001's retry loop then auto-promotes eligible Failed jobs
back to Pending. No new status enum, no schema migration.

- JobRepository.ListTimedOutAwaitingJobs with per-status cutoff WHERE
- JobService.ReapTimedOutJobs mirrors RetryFailedJobs structure
- Scheduler jobTimeoutLoop with atomic.Bool idempotency guard, 2m
  per-tick context, WaitGroup shutdown drain
- Config: CERTCTL_JOB_TIMEOUT_INTERVAL (10m), CERTCTL_JOB_AWAITING_CSR_TIMEOUT
  (24h), CERTCTL_JOB_AWAITING_APPROVAL_TIMEOUT (168h)
- Audit event per transition: actor=system, actorType=System,
  action=job_timeout, details={old_status, new_status, timeout_reason,
  age_hours}
- 14 new tests: 3 config, 7 service, 4 scheduler

internal/service/verification_test.go

@@ -77,6 +77,10 @@ func (m *mockVerificationJobRepo) ClaimPendingByAgentID(ctx context.Context, age
 	return nil, nil
 }
 
+func (m *mockVerificationJobRepo) ListTimedOutAwaitingJobs(ctx context.Context, csrCutoff, approvalCutoff time.Time) ([]*domain.Job, error) {
+	return nil, nil
+}
+
 // newVerificationTestService creates a VerificationService wired with test doubles.
 func newVerificationTestService(jobs map[string]*domain.Job, jobRepoErr error) (*VerificationService, *mockVerificationJobRepo, *mockAuditRepo) {
 	jobRepo := &mockVerificationJobRepo{jobs: jobs, err: jobRepoErr}