repo,service: introduce WithinTx and atomic audit rows for issue/renew/revoke

Closes the #3 acquisition-readiness blocker from the 2026-05-01 issuer
coverage audit (Part 1.5 finding #1: audit row not transactional with
issuance). AuditRepository.Create previously ran on the package-level
*sql.DB while the certificate insert / version insert / revocation
insert ran on independent connections — a failed audit INSERT after
a successful operation INSERT was silently lost. SOX §404 over IT
general controls, PCI-DSS §10 audit logging, HIPAA §164.312(b) audit
controls, and CA/B Forum Baseline Requirements §5.4.1 audit log
records all presume audit-with-operation atomicity.

Design — Option A (Querier abstraction). The chosen pattern: a shared
repository.Querier interface (subset of *sql.DB and *sql.Tx) plus a
postgres.WithinTx helper that begins a tx, runs fn, commits on nil
error, rolls back on error or panic, and returns the wrapped result.
Repository methods that participate in a service-layer transaction
expose a *WithTx variant taking repository.Querier; the bare methods
remain for stand-alone use. A repository.Transactor abstracts the
"begin tx, run fn, commit/rollback" lifecycle so service-layer code
runs multi-write operations atomically without holding *sql.DB
directly. Option B (UnitOfWork) was considered but adds boilerplate
without behavioral benefit for the current scope. Option C
(context-carried tx) was explicitly rejected — it hides the
transactional boundary from the type system, reproducing the class
of bug we're fixing.

This commit:
- Adds internal/repository/querier.go with the Querier interface
  (compile-time guards that *sql.DB and *sql.Tx satisfy it) and the
  Transactor interface for service-layer use.
- Adds internal/repository/postgres/tx.go with the WithinTx helper
  (begin/fn/commit/rollback with panic recovery) and a transactor
  type that satisfies repository.Transactor.
- Adds CreateWithTx variants on AuditRepository, CertificateRepository
  (Create + Update + CreateVersion), and RevocationRepository.
  Existing bare methods now delegate to the *WithTx variant using
  the package-level *sql.DB so existing call sites are
  behavior-preserving.
- Updates repository/interfaces.go: AuditRepository, CertificateRepository,
  and RevocationRepository declare the new *WithTx methods. Adds an
  atomicity contract doc-comment on AuditRepository pointing at
  WithinTx + the audit blocker.
- Adds AuditService.RecordEventWithTx, mirroring RecordEvent but
  routing through CreateWithTx so the audit row is part of the
  caller's transaction. Same redaction + marshalling contract.
- Refactors three audit-emitting service paths to use Transactor.WithinTx
  when SetTransactor was wired, with a legacy fallback for backward
  compat:
    * CertificateService.Create — cert insert + audit row in one tx.
    * RevocationSvc.RevokeCertificateWithActor — cert status update +
      revocation row + audit row in one tx. The OCSP cache invalidate
      remains best-effort (out of scope per the prompt).
    * RenewalService CompleteServerRenewal — cert version insert +
      cert update + audit row in one tx. Job status update stays
      outside the audit-atomicity scope (job state lives outside
      the operator-facing audit trail).
- Adds SetTransactor on CertificateService, RevocationSvc, and
  RenewalService. cmd/server/main.go wires a single Transactor
  instance shared across all three so all audit-emitting paths run
  their writes in transactions backed by the same *sql.DB handle.
- Updates 5 mock implementations to satisfy the new interface methods:
  mockCertRepo (testutil_test.go), mockCertRepoWithGetError
  (shortlived_test.go), fakeRevocationRepo (crl_cache_test.go),
  intuneE2EAuditRepo (scep_intune_e2e_test.go), and the integration-
  test mocks (lifecycle_test.go: mockCertificateRepository,
  mockAuditRepository, mockRevocationRepository). All *WithTx mocks
  ignore the Querier and delegate to the bare method (mocks have no
  DB; in-memory state is shared regardless of "tx").
- Adds a service-layer test mockTransactor with BeginTxErr and
  CommitErr knobs so the atomic-audit tests can assert error
  propagation through the transactional boundary.
- Adds internal/repository/postgres/tx_test.go: unit-level test that
  WithinTx surfaces "begin tx" wrap when BeginTx fails, and that
  Transactor.WithinTx delegates correctly. Real-Postgres rollback
  semantics are covered by the testcontainers tests in the postgres
  package — sandbox disk pressure prevented adding a sqlmock dep
  for the in-fn / commit-failure unit test, so those scenarios are
  exercised through atomic_audit_test.go using the mockTransactor's
  CommitErr / BeginTxErr fields.
- Adds internal/service/atomic_audit_test.go:
    * TestCertificateService_Create_AtomicWithTx — asserts audit
      insert failure inside the tx surfaces as the operation's error
      (closes the blocker contract).
    * TestCertificateService_Create_LegacyPathLogs — pins the
      backward-compat behavior when SetTransactor isn't wired:
      audit failure is logged-not-failed, matching pre-fix.
    * TestCertificateService_Create_TransactorBeginFailure — BeginTx
      error path: operation fails, no cert insert, no audit insert.
    * TestCertificateService_Create_TransactorCommitFailure —
      Commit error after successful in-fn writes surfaces as the
      operation's error. Real Postgres can fail Commit on
      serialization conflicts; the service must report this.

Out of scope (separate follow-up commits, same shape):
- Issuer CRUD audit atomicity.
- Target CRUD audit atomicity.
- Agent retire (already transactional via RetireAgentWithCascade;
  verified, not changed).
- Renewal-policy CRUD audit atomicity.
- Owner/team/agent-group CRUD audit atomicity.
- Discovery / health-check audit atomicity.

Verified locally:
- gofmt -l . clean
- go vet ./... clean
- staticcheck ./... clean
- golangci-lint run --timeout 5m ./... → 0 issues
- go test -short -count=1 ./internal/service/ green
- go test -short -count=1 ./internal/api/handler/ green
- go test -short -count=1 ./internal/integration/ green
- go test -short -count=1 ./internal/repository/postgres/ green
- go build ./... success

Audit reference: cowork/issuer-coverage-audit-2026-05-01/RESULTS.md
Top-10 fix #3 (Part 3, narrative section).

internal/repository/postgres/certificate.go

@@ -313,7 +313,19 @@ func (r *CertificateRepository) GetByIssuerAndSerial(ctx context.Context, issuer
 }
 
 // Create stores a new certificate
+// Create stores a new certificate using the repository's package-level
+// *sql.DB. Use CreateWithTx when the cert insert must be atomic with
+// another database operation in a service-layer transaction (typically
+// the audit row for issuance).
 func (r *CertificateRepository) Create(ctx context.Context, cert *domain.ManagedCertificate) error {
+	return r.CreateWithTx(ctx, r.db, cert)
+}
+
+// CreateWithTx stores a new certificate using the supplied Querier.
+// Pass *sql.Tx (typically from postgres.WithinTx) to participate in a
+// caller's transaction; pass *sql.DB or call Create for stand-alone
+// inserts. Closes the audit-atomicity blocker for the issuance path.
+func (r *CertificateRepository) CreateWithTx(ctx context.Context, q repository.Querier, cert *domain.ManagedCertificate) error {
 	if cert.ID == "" {
 		cert.ID = uuid.New().String()
 	}
@@ -333,7 +345,7 @@ func (r *CertificateRepository) Create(ctx context.Context, cert *domain.Managed
 		revocationReason = &cert.RevocationReason
 	}
 
-	err = r.db.QueryRowContext(ctx, `
+	err = q.QueryRowContext(ctx, `
 		INSERT INTO managed_certificates (
 			id, name, common_name, sans, environment, owner_id, team_id, issuer_id, renewal_policy_id,
 			certificate_profile_id, status, expires_at, tags, last_renewal_at, last_deployment_at, revoked_at, revocation_reason, source, created_at, updated_at
@@ -353,8 +365,19 @@ func (r *CertificateRepository) Create(ctx context.Context, cert *domain.Managed
 	return nil
 }
 
-// Update modifies an existing certificate
+// Update modifies an existing certificate using the repository's
+// package-level *sql.DB. Use UpdateWithTx when the cert update must be
+// atomic with another database operation (typically a revocation row +
+// audit row).
 func (r *CertificateRepository) Update(ctx context.Context, cert *domain.ManagedCertificate) error {
+	return r.UpdateWithTx(ctx, r.db, cert)
+}
+
+// UpdateWithTx modifies an existing certificate using the supplied
+// Querier. Closes the audit-atomicity blocker for the revocation path
+// (cert status update must be atomic with the revocation_events insert
+// + audit row insert).
+func (r *CertificateRepository) UpdateWithTx(ctx context.Context, q repository.Querier, cert *domain.ManagedCertificate) error {
 	tagsJSON, err := json.Marshal(cert.Tags)
 	if err != nil {
 		return fmt.Errorf("failed to marshal tags: %w", err)
@@ -370,7 +393,7 @@ func (r *CertificateRepository) Update(ctx context.Context, cert *domain.Managed
 		revocationReason = &cert.RevocationReason
 	}
 
-	result, err := r.db.ExecContext(ctx, `
+	result, err := q.ExecContext(ctx, `
 		UPDATE managed_certificates SET
 			name = $1,
 			common_name = $2,
@@ -471,13 +494,23 @@ func (r *CertificateRepository) ListVersions(ctx context.Context, certID string)
 	return versions, nil
 }
 
-// CreateVersion stores a new certificate version
+// CreateVersion stores a new certificate version using the repository's
+// package-level *sql.DB. Use CreateVersionWithTx when the version
+// insert must be atomic with another database operation (typically the
+// audit row for renewal).
 func (r *CertificateRepository) CreateVersion(ctx context.Context, version *domain.CertificateVersion) error {
+	return r.CreateVersionWithTx(ctx, r.db, version)
+}
+
+// CreateVersionWithTx stores a new certificate version using the
+// supplied Querier. Closes the audit-atomicity blocker for the
+// renewal path (new version row must be atomic with the audit row).
+func (r *CertificateRepository) CreateVersionWithTx(ctx context.Context, q repository.Querier, version *domain.CertificateVersion) error {
 	if version.ID == "" {
 		version.ID = uuid.New().String()
 	}
 
-	err := r.db.QueryRowContext(ctx, `
+	err := q.QueryRowContext(ctx, `
 		INSERT INTO certificate_versions (
 			id, certificate_id, serial_number, not_before, not_after,
 			fingerprint_sha256, pem_chain, csr_pem, key_algorithm, key_size, created_at