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-functions/api-test-install.md

@@ -0,0 +1,22 @@
+testInstall()
+
+checks Smarty installation
+
+Description
+===========
+
+void
+
+testInstall
+
+This function verifies that all required working folders of the Smarty
+installation can be accessed. It does output a corresponding protocol.
+
+
+    <?php
+    require_once('Smarty.class.php');
+    $smarty  = new Smarty();
+    $smarty->testInstall();
+    ?>
+
+