Format code with Black and isort for CI/CD compliance

- Apply Black formatting to all Python files in core and stiftung modules
- Fix import statement ordering with isort
- Ensure all code meets automated quality standards
- Resolve CI/CD pipeline formatting failures
- Maintain consistent code style across the entire codebase

app/core/celery.py

@@ -1,4 +1,5 @@
 import os
+
 from celery import Celery
 
 os.environ.setdefault("DJANGO_SETTINGS_MODULE", "core.settings")
@@ -6,5 +7,3 @@ os.environ.setdefault("DJANGO_SETTINGS_MODULE", "core.settings")
 app = Celery("core")
 app.config_from_object("django.conf:settings", namespace="CELERY")
 app.autodiscover_tasks()
-
-