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

backend/src/snapshots/snapshots.service.ts

@@ -287,7 +287,8 @@ export class SnapshotsService {
 
   /**
    * Rollback an application to a specific snapshot.
-   * Restores: source code, wp-content (WordPress), and database.
+   * Uses K8s revision rollback for the app deployment (instant, no rebuild).
+   * File-based restore for DB dump and wp-content.
    */
   async rollbackToSnapshot(snapshotId: string, userId: string): Promise<{ success: boolean; details: string[] }> {
     const snapshot = await this.findOne(snapshotId, userId);
@@ -299,20 +300,45 @@ export class SnapshotsService {
     const app = await this.applicationsService.findOne(snapshot.applicationId, userId);
     const details: string[] = [];
 
-    // 1. Restore source code
-    if (snapshot.appArchivePath && fs.existsSync(snapshot.appArchivePath)) {
-      const uploadDir = this.configService.get<string>('platform.uploadDir') || './uploads';
-      const appDir = path.join(uploadDir, app.userId, app.id);
-      const destPath = path.join(appDir, 'source.zip');
-      fs.mkdirSync(appDir, { recursive: true });
-      fs.copyFileSync(snapshot.appArchivePath, destPath);
-      // Update app codePath in DB
-      await this.applicationsService.update(app.id, app.userId, { codePath: destPath } as any);
-      details.push('✅ Source code restored');
-      this.logger.log(`Rollback ${snapshotId}: restored source code`);
+    // 1. Rollback K8s Deployment via revision (instant — no rebuild)
+    //    Find the revision that matches the snapshot's imageTag
+    if (snapshot.imageTag) {
+      try {
+        const { revisions } = await this.kubernetesService.getDeploymentRevisions(app);
+        const targetRevision = revisions.find((r) => r.image === snapshot.imageTag);
+
+        if (targetRevision && !targetRevision.isCurrent) {
+          const result = await this.kubernetesService.rollbackDeploymentRevision(app, targetRevision.revision);
+          if (result.success) {
+            details.push(`✅ App rolled back to K8s revision ${targetRevision.revision} (instant)`);
+            this.logger.log(`Rollback ${snapshotId}: K8s revision rollback to ${targetRevision.revision}`);
+          } else {
+            details.push(`⚠️ K8s revision rollback failed: ${result.message}`);
+          }
+        } else if (targetRevision?.isCurrent) {
+          details.push('ℹ️ App is already running the snapshot\'s image — no deployment change needed');
+        } else {
+          // Revision not found — fall back to restoring source code and redeploying
+          if (snapshot.appArchivePath && fs.existsSync(snapshot.appArchivePath)) {
+            const uploadDir = this.configService.get<string>('platform.uploadDir') || './uploads';
+            const appDir = path.join(uploadDir, app.userId, app.id);
+            const destPath = path.join(appDir, 'source.zip');
+            fs.mkdirSync(appDir, { recursive: true });
+            fs.copyFileSync(snapshot.appArchivePath, destPath);
+            await this.applicationsService.update(app.id, app.userId, { codePath: destPath } as any);
+            details.push('✅ Source code restored (K8s revision expired — will need redeploy)');
+            this.logger.log(`Rollback ${snapshotId}: source code restored (revision not found)`);
+          } else {
+            details.push('⚠️ K8s revision not found and no source archive available');
+          }
+        }
+      } catch (e: any) {
+        this.logger.warn(`Rollback ${snapshotId}: K8s revision rollback error — ${e.message}`);
+        details.push(`⚠️ K8s rollback failed: ${e.message}`);
+      }
     }
 
-    // 2. Restore wp-content (WordPress)
+    // 2. Restore wp-content (WordPress) — file-based
     if (snapshot.wpContentArchivePath && fs.existsSync(snapshot.wpContentArchivePath)) {
       const archiveBuffer = fs.readFileSync(snapshot.wpContentArchivePath);
       const result = await this.kubernetesService.restoreWpContent(app, archiveBuffer);
@@ -325,7 +351,7 @@ export class SnapshotsService {
       }
     }
 
-    // 3. Restore database
+    // 3. Restore database — file-based
     if (snapshot.dbDumpPath && fs.existsSync(snapshot.dbDumpPath)) {
       const dumpBuffer = fs.readFileSync(snapshot.dbDumpPath);
       const result = await this.kubernetesService.restoreDatabaseDump(app, dumpBuffer);
@@ -345,6 +371,27 @@ export class SnapshotsService {
     return { success: true, details };
   }
 
+  /**
+   * Rollback using K8s revision directly (without a snapshot).
+   * Fastest rollback — just switches the active ReplicaSet.
+   */
+  async rollbackToRevision(
+    applicationId: string,
+    userId: string,
+    targetRevision: number,
+  ): Promise<{ success: boolean; message: string }> {
+    const app = await this.applicationsService.findOne(applicationId, userId);
+    return this.kubernetesService.rollbackDeploymentRevision(app, targetRevision);
+  }
+
+  /**
+   * Get K8s deployment revisions for an application.
+   */
+  async getRevisions(applicationId: string, userId: string) {
+    const app = await this.applicationsService.findOne(applicationId, userId);
+    return this.kubernetesService.getDeploymentRevisions(app);
+  }
+
   /**
    * Delete a specific snapshot.
    */