feat(M34): dynamic issuer configuration with encrypted config storage

Replace static env-var-based issuer wiring with GUI-driven dynamic
configuration stored encrypted in PostgreSQL. Operators can now
configure, test, enable/disable, and manage issuers from the dashboard
without restarting the server.

Key changes:
- AES-256-GCM encryption for sensitive issuer config at rest (PBKDF2
  key derivation with 100k iterations)
- Dynamic IssuerRegistry with sync.RWMutex replacing static map
- Connector factory pattern (issuerfactory.NewFromConfig) replacing
  140 lines of static wiring in main.go
- Migration 000009: encrypted_config, last_tested_at, test_status,
  source columns on issuers table
- Env var seeding on first boot with ON CONFLICT DO NOTHING
- Registry Rebuild() for atomic map swap after CRUD operations
- Issuer type validation against domain constants on Create
- Audit trail for test connection results
- Conditional seeding for step-ca/OpenSSL (only when env vars set)
- GUI: source badge, connection test status on issuer detail page

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/service/revocation_test.go

@@ -2,6 +2,7 @@ package service
 
 import (
 	"context"
+	"log/slog"
 	"testing"
 	"time"
 
@@ -21,15 +22,13 @@ func newRevocationTestService() (*CertificateService, *mockCertRepo, *mockRevoca
 
 	// Create RevocationSvc
 	revSvc := NewRevocationSvc(certRepo, revocationRepo, auditService)
-	revSvc.SetIssuerRegistry(map[string]IssuerConnector{
-		"iss-local": &mockIssuerConnector{},
-	})
+	registry := NewIssuerRegistry(slog.Default())
+	registry.Set("iss-local", &mockIssuerConnector{})
+	revSvc.SetIssuerRegistry(registry)
 
 	// Create CAOperationsSvc
 	caSvc := NewCAOperationsSvc(revocationRepo, certRepo, profileRepo)
-	caSvc.SetIssuerRegistry(map[string]IssuerConnector{
-		"iss-local": &mockIssuerConnector{},
-	})
+	caSvc.SetIssuerRegistry(registry)
 
 	certService := NewCertificateService(certRepo, policyService, auditService)
 	certService.SetRevocationSvc(revSvc)
@@ -243,9 +242,9 @@ func TestRevokeCertificate_WithIssuerNotification(t *testing.T) {
 
 	// Wire up issuer registry on RevocationSvc with mock
 	mockIssuer := &mockIssuerConnector{}
-	svc.revSvc.SetIssuerRegistry(map[string]IssuerConnector{
-		"iss-local": mockIssuer,
-	})
+	registry := NewIssuerRegistry(slog.Default())
+	registry.Set("iss-local", mockIssuer)
+	svc.revSvc.SetIssuerRegistry(registry)
 
 	cert := &domain.ManagedCertificate{
 		ID:         "cert-7",