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-plugins-dir.md

@@ -0,0 +1,28 @@
+\$plugins\_dir {#variable.plugins.dir}
+==============
+
+This is the directory or directories where Smarty will look for the
+plugins that it needs. Default is `plugins/` under the
+[`SMARTY_DIR`](#constant.smarty.dir). If you supply a relative path,
+Smarty will first look under the [`SMARTY_DIR`](#constant.smarty.dir),
+then relative to the current working directory, then relative to the PHP
+include\_path. If `$plugins_dir` is an array of directories, Smarty will
+search for your plugin in each plugin directory **in the order they are
+given**.
+
+> **Note**
+>
+> For best performance, do not setup your `$plugins_dir` to have to use
+> the PHP include path. Use an absolute pathname, or a path relative to
+> `SMARTY_DIR` or the current working directory.
+
+> **Note**
+>
+> As of Smarty 3.1 the attribute \$plugins\_dir is no longer accessible
+> directly. Use [`getPluginsDir()`](#api.get.plugins.dir),
+> [`setPluginsDir()`](#api.set.plugins.dir) and
+> [`addPluginsDir()`](#api.add.plugins.dir) instead.
+
+See also [`getPluginsDir()`](#api.get.plugins.dir),
+[`setPluginsDir()`](#api.set.plugins.dir) and
+[`addPluginsDir()`](#api.add.plugins.dir).