Add Creative Elements templates and update index files

- Introduced new templates for catalog, checkout, contact, and error pages.
- Implemented caching headers and redirection in index.php files across various directories.
- Enhanced product and layout templates for better integration with Creative Elements.
- Added backoffice header styles and scripts for improved UI/UX in the admin panel.

modules/creativeelements/modifications.txt

@@ -0,0 +1,15 @@
+1. ############ disabled code because of unability to import templates automatically
+
+file: /core/base/document.php
+
+461: //if (!$this->isEditableByCurrentUser()) {
+462: //     return false;
+463: //}
+
+
+2. ########### change export file name
+
+file: /includes/template-library/sources/local.php
+
+794: 'name' => $post->post_title. '.json',
+