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/views/templates/front/theme/errors/404.tpl

@@ -0,0 +1,22 @@
+{**
+ * Creative Elements - live Theme & Page Builder
+ *
+ * @author    WebshopWorks
+ * @copyright 2019-2022 WebshopWorks.com
+ * @license   One domain support license
+ *}
+{if isset($CE_PAGE_NOT_FOUND)}
+	{$ce_layout=$layout}
+{elseif file_exists("{$smarty.const._PS_THEME_DIR_}templates/errors/404.tpl")}
+	{$ce_layout='[1]errors/404.tpl'}
+{elseif $smarty.const._PARENT_THEME_NAME_}
+	{$ce_layout='parent:errors/404.tpl'}
+{/if}
+
+{extends $ce_layout}
+
+{if isset($CE_PAGE_NOT_FOUND)}
+	{block name='content'}
+	<section id="content">{$CE_PAGE_NOT_FOUND|cefilter}</section>
+	{/block}
+{/if}