feat: complete E2E deployment flow with storage layered config and values template versioning

- Instance deployment: charts browser, deploy modal, instances list
- Values Template version management (create/history/rollback)
- Storage layered config (cluster > workspace > shared priority)
- Cluster credential decryptIfNeeded for mixed encrypted/plaintext kubeconfig
- YAML syntax validation (client-side + server-side warning)
- Frontend: charts, instances, storage, templates, admin pages
- Backend: storage service, instance service, cluster service, helm client
- Multi-Tenant Kubeconfig.md: added by user

backend/internal/adapter/output/persistence/mock/storage_repository_mock.go

@@ -83,7 +83,28 @@ func (r *StorageRepositoryMock) GetDefault(ctx context.Context, workspaceID stri
 			return s, nil
 		}
 	}
-	return nil, entity.ErrStorageNotFound
+	return nil, nil
+}
+
+// GetByCluster 获取 cluster 关联的存储后端
+func (r *StorageRepositoryMock) GetByCluster(ctx context.Context, clusterID string) ([]*entity.StorageBackend, error) {
+	var result []*entity.StorageBackend
+	for _, s := range r.storages {
+		if s.ClusterID == clusterID {
+			result = append(result, s)
+		}
+	}
+	return result, nil
+}
+
+// GetDefaultByCluster 获取 cluster 的默认存储后端
+func (r *StorageRepositoryMock) GetDefaultByCluster(ctx context.Context, clusterID string) (*entity.StorageBackend, error) {
+	for _, s := range r.storages {
+		if s.ClusterID == clusterID && s.IsDefault {
+			return s, nil
+		}
+	}
+	return nil, nil
 }
 
 // List 列出所有存储（管理员用）