feat: use Kubernetes revision-based rollback for instant app rollback

- Add revisionHistoryLimit: 10 and change-cause annotation to K8s deployments
- Add getDeploymentRevisions() to list ReplicaSet revision history
- Add rollbackDeploymentRevision() using K8s API (instant, no rebuild)
- Refactor snapshot rollback: use K8s revision for app, keep file-based DB/wp-content restore
- Add GET /snapshots/applications/:appId/revisions endpoint
- Add POST /snapshots/applications/:appId/revisions/:rev/rollback endpoint
- Add K8sRevision and K8sRevisionData types to frontend
- Redesign UI with two tabs: K8s Revisions (instant) + File Snapshots (full backup)
- K8s Revisions tab shows deployment history with one-click instant rollback
- File Snapshots tab retains download, DB restore, and wp-content restore

frontend/src/types/index.ts

@@ -311,3 +311,17 @@ export interface AppSnapshot {
   createdBy: string;
   createdAt: string;
 }
+
+export interface K8sRevision {
+  revision: number;
+  image: string;
+  changeCause: string;
+  createdAt: string;
+  replicas: number;
+  isCurrent: boolean;
+}
+
+export interface K8sRevisionData {
+  revisions: K8sRevision[];
+  currentRevision: number;
+}