fix(deploy): persist replica snapshot before stop for restore on start

Read live deployment replica counts from K8s before scaling to zero,
store them on the application as suspendedReplicas, and use that snapshot
when resuming so Start restores the pre-stop replica layout.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/applications/applications.service.ts

@@ -189,6 +189,25 @@ export class ApplicationsService {
     return this.appsRepository.save(app);
   }
 
+  async saveSuspendedReplicas(
+    id: string,
+    snapshot: Record<string, number>,
+  ): Promise<Application> {
+    const app = await this.findOne(id);
+    app.suspendedReplicas = snapshot;
+    app.suspendedAt = new Date();
+    if (snapshot[app.name] !== undefined) {
+      app.replicas = snapshot[app.name];
+    }
+    return this.appsRepository.save(app);
+  }
+
+  async clearSuspendedReplicas(id: string): Promise<Application> {
+    const app = await this.findOne(id);
+    app.suspendedReplicas = undefined;
+    return this.appsRepository.save(app);
+  }
+
   async uploadCode(id: string, userId: string, file: Express.Multer.File): Promise<Application> {
     if (!file) {
       throw new BadRequestException('No file uploaded');