Enhance product management and coupon features

- Added styling for input group add-ons and additional fields in SCSS.
- Updated shop coupon view to include a new column for usage count.
- Display coupon code and amount in order details if applicable.
- Improved product edit template to handle custom fields with required validation.
- Modified product save logic to include custom field requirements.
- Enhanced decimal normalization function for better input handling.
- Implemented checkbox normalization for form submissions.
- Updated custom fields in product templates to reflect required status.
- Fixed URL for fetching changelog updates.

admin/templates/update/main-view.php

@@ -64,7 +64,7 @@ echo $grid -> draw();
 ?>
 <?
 ob_start();
-echo $versions = file_get_contents( 'https://shoppro.project-dc.pl/updates/changelog.php' );
+echo $versions = file_get_contents( 'http://www.shoppro.project-dc.pl/updates/changelog.php' );
 $out = ob_get_clean();
 
 $grid                    = new \gridEdit;