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_svc_test.go

@@ -4,6 +4,7 @@ package service
 
 import (
 	"context"
+	"log/slog"
 	"testing"
 	"time"
 
@@ -18,9 +19,9 @@ func newRevocationSvcTest() (*RevocationSvc, *mockCertRepo, *mockRevocationRepo,
 
 	auditService := NewAuditService(auditRepo)
 	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)
 
 	return revSvc, certRepo, revocationRepo, auditRepo
 }