Refactor(backend): improve formatting in services, repositories & tests

- Consistently format multi-line function headers, exception handling, and repository method calls for readability.
- Reorganize misplaced imports across modules (e.g., services & tests) into proper sorted order.
- Adjust indentation, line breaks, and spacing inconsistencies in tests and migration files.
- Cleanup unnecessary trailing newlines and reorganize `__all__` declarations for consistency.

backend/app/alembic/env.py

@@ -40,6 +40,7 @@ def include_object(object, name, type_, reflected, compare_to):
             return False
     return True
 
+
 # Interpret the config file for Python logging.
 # This line sets up loggers basically.
 if config.config_file_name is not None: