Refactor Zasilkovna client, update imports and cleanup

Refactored the Zasilkovna SOAP client to use a singleton pattern with caching and lazy loading, improving reliability and startup performance. Updated invoice PDF generation to import WeasyPrint lazily, preventing startup failures on systems missing dependencies. Cleaned up unused imports and code in several frontend components, removed unused state and variables, and adjusted Docker frontend port mapping. Also updated Django migration files to reflect a new generation timestamp.

backend/commerce/tasks.py

@@ -5,6 +5,10 @@ from django.apps import apps
 from django.utils import timezone
 
 
+# -- CLEANUP TASKS --
+
+# Delete expired/cancelled orders (older than 24 hours)
+@shared_task
 def delete_expired_orders():
     Order = apps.get_model('commerce', 'Order')