style: standardize string formatting and improve readability across multiple files

- Refactored string formatting in various files to use consistent double quotes.
- Improved readability by adding newlines in function definitions and method calls.
- Cleaned up unnecessary imports and ensured proper spacing for better code clarity.
- Updated management commands and context processors for consistent formatting.
- Enhanced the overall maintainability of the codebase by adhering to PEP 8 guidelines.
- Applied Ruff linting and formatting

src/pkmntrade_club/django_project/__init__.py

@@ -2,4 +2,4 @@
 # Django starts so that shared_task will use this app.
 from .celery import app as celery_app
 
-__all__ = ('celery_app',)
+__all__ = ("celery_app",)