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.md

@@ -0,0 +1,44 @@
+Extending Smarty With Plugins {#plugins}
+=============================
+
+## Table of contents
+
+- [How Plugins Work](./plugins/plugins-howto.md)
+- [Naming Conventions](./plugins/plugins-naming-conventions.md) 
+- [Writing Plugins](./plugins/plugins-writing.md) 
+- [Template Functions](./plugins/plugins-functions.md) 
+- [Modifiers](./plugins/plugins-modifiers.md)
+- [Block Functions](./plugins/plugins-block-functions.md) 
+- [Compiler Functions](./plugins/plugins-compiler-functions.md) 
+- [Prefilters/Postfilters](./plugins/plugins-prefilters-postfilters.md)
+- [Output Filters](./plugins/plugins-outputfilters.md) 
+- [Resources](./plugins/plugins-resources.md)
+- [Inserts](./plugins/plugins-inserts.md)
+
+Version 2.0 introduced the plugin architecture that is used for almost
+all the customizable functionality of Smarty. This includes:
+
+-   functions
+
+-   modifiers
+
+-   block functions
+
+-   compiler functions
+
+-   prefilters
+
+-   postfilters
+
+-   outputfilters
+
+-   resources
+
+-   inserts
+
+With the exception of resources, backwards compatibility with the old
+way of registering handler functions via register\_\* API is preserved.
+If you did not use the API but instead modified the class variables
+`$custom_funcs`, `$custom_mods`, and other ones directly, then you will
+need to adjust your scripts to either use the API or convert your custom
+functionality into plugins.