Changes include:
- Updated `AbstractOrderingStep.php` to handle null case in `getOrder` method and modified return
type.
- Refactored `Order.php` to remove unnecessary checks and improve readability.
- Ensured safety against calling non-existent `save()` method in `Checkout.php`.
- Simplified address getting logic in `CustomerData.php`.
- Removed unnecessary check in isUserB2B function.

Related: #172

Improve readability and interpretability of code by explicitly stating null in union types. This
change has been applied across multiple files and functions.

PHP8.4 compatibility

Related: order-guestorder#6

Related: order-guestorder#6

Related: quiqqer/order#163

The UX was not optimal as a result. It was not clear that you could scroll and the guest order button was not visible.
For now flex removed and the login buttons are below each other

Related: template-cologne#111

(cherry picked from commit 065225a2)

Co-authored-by: Michael Danielczok <michael@pcsg.de>