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/api-variables/variable-allow-php-templates.md

@@ -0,0 +1,18 @@
+\$allow\_php\_templates {#variable.allow.php.templates}
+=======================
+
+By default the PHP template file resource is disabled. Setting
+`$allow_php_templates` to TRUE will enable PHP template files.
+
+::: {.informalexample}
+
+    <?php
+    $smarty->allow_php_templates = true;
+    ?>
+
+            
+:::
+
+> **Note**
+>
+> The PHP template file resource is an undocumented deprecated feature.