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-config-booleanize.md

@@ -0,0 +1,8 @@
+\$config\_booleanize {#variable.config.booleanize}
+====================
+
+If set to TRUE, [config files](#config.files) values of `on/true/yes`
+and `off/false/no` get converted to boolean values automatically. This
+way you can use the values in the template like so:
+`{if #foobar#}...{/if}`. If foobar was `on`, `true` or `yes`, the `{if}`
+statement will execute. Defaults to TRUE.