refactor: full-stack restructure with multi-tenancy, workspace management, and K8s diagnostics

- Add Workspace domain (entity, repository, service, handler, DTO)
- Add multi-tenant K8s client with tenant binding and quota management
- Add K8s diagnostics client (instance diagnostics)
- Add authorization middleware (authz package)
- Restructure frontend to feature-based architecture (features/)
- Add User Management page in configuration
- Add AccessDenied page and route guards
- Refactor shared components (form inputs, layout, UI)
- Update Tailwind config for new design system
- Add comprehensive documentation (docs/, tasks/, plans)
- Improve cluster service with better kubeconfig handling
- Add tests for crypto, config, helm client, tenant binding

backend/internal/pkg/crypto/crypto_test.go

@@ -12,7 +12,7 @@ func TestAESEncryptor(t *testing.T) {
 		plaintext string
 	}{
 		{"simple password", "password123"},
-		{"harbor password", "BWGDIP@ssw0rd1401#"},
+		{"registry password", "registry-password-example"},
 		{"empty string", ""},
 		{"long certificate", "LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSUJkekNDQVIyZ0F3SUJBZ0lCQURBS0JnZ3Foa2pP"},
 		{"unicode", "密码123!@#"},
@@ -121,4 +121,3 @@ func TestEncryptionConsistency(t *testing.T) {
 		t.Error("Decryption should produce original plaintext")
 	}
 }
-