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-cache-id.md

@@ -0,0 +1,11 @@
+\$cache\_id {#variable.cache.id}
+===========
+
+Persistent cache\_id identifier. As an alternative to passing the same
+`$cache_id` to each and every function call, you can set this
+`$cache_id` and it will be used implicitly thereafter.
+
+With a `$cache_id` you can have multiple cache files for a single call
+to [`display()`](#api.display) or [`fetch()`](#api.fetch) depending for
+example from different content of the same template. See the [caching
+section](#caching) for more information.