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/plugins/plugins-naming-conventions.md

@@ -0,0 +1,51 @@
+Naming Conventions {#plugins.naming.conventions}
+==================
+
+Plugin files and functions must follow a very specific naming convention
+in order to be located by Smarty.
+
+**plugin files** must be named as follows:
+
+> `
+>         type.name.php
+>        `
+
+-   Where `type` is one of these plugin types:
+
+    -   function
+
+    -   modifier
+
+    -   block
+
+    -   compiler
+
+    -   prefilter
+
+    -   postfilter
+
+    -   outputfilter
+
+    -   resource
+
+    -   insert
+
+-   And `name` should be a valid identifier; letters, numbers, and
+    underscores only, see [php
+    variables](https://www.php.net/language.variables).
+
+-   Some examples: `function.html_select_date.php`, `resource.db.php`,
+    `modifier.spacify.php`.
+
+**plugin functions** inside the PHP files must be named as follows:
+
+> `smarty_type_name`
+
+-   The meanings of `type` and `name` are the same as above.
+
+-   An example modifier name `foo` would be
+    `function smarty_modifier_foo()`.
+
+Smarty will output appropriate error messages if the plugin file it
+needs is not found, or if the file or the plugin function are named
+improperly.