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-debug-template.md

@@ -0,0 +1,9 @@
+\$debug\_tpl {#variable.debug_template}
+============
+
+This is the name of the template file used for the debugging console. By
+default, it is named `debug.tpl` and is located in the
+[`SMARTY_DIR`](#constant.smarty.dir).
+
+See also [`$debugging`](#variable.debugging) and the [debugging
+console](#chapter.debugging.console) section.