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/dto/application.dto.ts

@@ -57,6 +57,11 @@ export class CreateApplicationDto {
   @IsString()
   dbPassword?: string;
 
+  @ApiPropertyOptional({ example: '1Gi', description: 'Database PVC storage size (e.g. 1Gi, 5Gi, 10Gi). Default: 1Gi' })
+  @IsOptional()
+  @IsString()
+  dbStorageSize?: string;
+
   @ApiPropertyOptional({ example: 'https://github.com/user/repo.git' })
   @IsOptional()
   @IsString()