Refactor Stripe payment handling and order status

Refactored Stripe payment integration to use a dedicated Stripe model for session data, updating the PaymentSerializer accordingly. Renamed Order.Status to Order.OrderStatus for clarity. Updated configuration app to ensure SiteConfiguration singleton is created post-migration. Removed obsolete seed_app_config command from docker-compose. Adjusted frontend API generated files and moved orval config.

backend/configuration/apps.py

@@ -1,21 +1,22 @@
 from django.apps import AppConfig
-from django.db.utils import OperationalError, ProgrammingError
+from django.db.models.signals import post_migrate
+
+def create_site_config(sender, **kwargs):
+    """
+    Ensure the SiteConfiguration singleton exists after migrations.
+    """
+    from .models import SiteConfiguration
+    try:
+        SiteConfiguration.get_solo()
+    except Exception:
+        pass
 
 class ConfigurationConfig(AppConfig):
     default_auto_field = 'django.db.models.BigAutoField'
     name = 'configuration'
 
     def ready(self):
-        """Ensure the SiteConfiguration singleton exists at startup.
-        Wrapped in broad DB error handling so that commands like
-        makemigrations/migrate don't fail when the table does not yet exist.
-        """
-        try:
-            from .models import SiteConfiguration  # local import to avoid premature app registry access
-            SiteConfiguration.get_solo()  # creates if missing
-            
-        except (OperationalError, ProgrammingError):
-            # DB not ready (e.g., before initial migrate); ignore silently
-            pass
+        # Spustí create_site_config po dokončení migrací
+        post_migrate.connect(create_site_config, sender=self)