fix(build): use kubectl cp for reliable source upload and fix Python/Django CMD

- Replace k8s.Exec WebSocket with kubectl cp for binary file transfer to PVC
- Fix Python Dockerfile CMD: switch from JSON exec form to shell form to avoid
  invalid JSON escape sequences (\|) causing shell parse errors
- Fix Django Dockerfile CMD with same shell form approach
- Add retry logic for ECONNRESET during build job polling
- Update seed.ts default admin email to match actual database

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

backend/src/seed.ts

@@ -14,14 +14,14 @@ import { UserRole } from './common/enums';
  *   npm run seed
  * 
  * Environment variables (or defaults):
- *   ADMIN_EMAIL=admin@cloudhost.local
+ *   ADMIN_EMAIL=test@example.com
  *   ADMIN_PASSWORD=Admin123!
  */
 async function bootstrap() {
   const app = await NestFactory.createApplicationContext(AppModule);
   const usersService = app.get(UsersService);
 
-  const email = process.env.ADMIN_EMAIL || 'admin@cloudhost.local';
+  const email = process.env.ADMIN_EMAIL || 'test@example.com';
   const password = process.env.ADMIN_PASSWORD || 'Admin123!';
 
   const existing = await usersService.findByEmail(email);