Dev-Umgebung: Kompatibilität für PHP 8.3 + Smarty 4.5.6

- Smarty 4.1.1 → 4.5.6 (behebt dynamic property deprecations)
- Core-Klassen: #[\AllowDynamicProperties] für Admin_role, base, Config,
  Customer, Customer_group, CustomerGroups, Item, Structure, website
- website.class.php: counts[parent_id] initialisieren vor ++ (PHP 8.1)
- layout.class.php: HTTP_ACCEPT_LANGUAGE mit isset-Guard
- website_init.php: session_status()-Check vor session_start
- .htaccess: HTTPS-Redirect via X-Forwarded-Proto (statt SERVER_PORT)
- themes/easyshop_advanced/media/: Parent-Theme-Assets nachgezogen
- .gitignore: smarty.4.1.1.bak ausschließen

libs/smarty/docs/programmers/resources/resources-extends.md

@@ -0,0 +1,36 @@
+Extends Template Resources {#resources.extends}
+==========================
+
+The `extends:` resource is used to define child/parent relationships for
+template inheritance from the PHP script. For details see section of
+[Template Inheritance](#advanced.features.template.inheritance).
+
+As of Smarty 3.1 the `extends:` resource may use any available [template
+resource](#resources), including `string:` and `eval:`. When [templates
+from strings](#resources.string) are used, make sure they are properly
+(url or base64) encoded. Is an `eval:` resource found within an
+inheritance chain, its \"don\'t save a compile file\" property is
+superseded by the `extends:` resource. The templates within an
+inheritance chain are not compiled separately, though. Only a single
+compiled template will be generated.
+
+> **Note**
+>
+> Use this when inheritance is required programmatically. When inheriting
+> within PHP, it is not obvious from the child template what inheritance
+> took place. If you have a choice, it is normally more flexible and
+> intuitive to handle inheritance chains from within the templates.
+
+
+    <?php
+    $smarty->display('extends:parent.tpl|child.tpl|grandchild.tpl'); 
+
+    // inheritance from multiple template sources
+    $smarty->display('extends:db:parent.tpl|file:child.tpl|grandchild.tpl|eval:{block name="fooBazVar_"}hello world{/block}'); 
+    ?>
+
+      
+
+See also [Template Inheritance](#advanced.features.template.inheritance)
+[`{block}`](#language.function.block) and
+[`{extends}`](#language.function.extends).