feat: dynamic database storage size with PVC expansion

- Add dbStorageSize column to Application entity (default: 1Gi)
- Add dbStorageSize to CreateApplicationDto, frontend types
- Use dynamic storage size in K8s deployDatabase instead of hardcoded 5Gi
- Deploy page: storage size selector with +/- buttons (min 1GB, max 100GB)
- Auto-suggest storage based on DB dump file size (3x dump size, min 1GB)
- Show DB storage in Review step
- App detail: Database Storage section with expand button
- GET /applications/:id/db-storage — read current PVC size from K8s
- PATCH /applications/:id/db-storage — expand PVC (only increase, no shrink)
- PVC resize uses JSON patch on K8s API

backend/src/applications/entities/application.entity.ts

@@ -44,6 +44,9 @@ export class Application {
   @Column({ nullable: true })
   dbPassword: string;
 
+  @Column({ nullable: true, default: '1Gi' })
+  dbStorageSize: string; // PVC storage size for database (e.g. '1Gi', '5Gi', '10Gi')
+
   @Column({ nullable: true })
   gitUrl: string;