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/designers/language-basic-syntax/language-syntax-attributes.md

@@ -0,0 +1,49 @@
+# Attributes
+
+Most of the [functions](./language-syntax-functions.md) take attributes that
+specify or modify their behavior. Attributes to Smarty functions are
+much like HTML attributes. Static values don't have to be enclosed in
+quotes, but it is required for literal strings. Variables with or
+without modifiers may also be used, and should not be in quotes. You can
+even use PHP function results, plugin results and complex expressions.
+
+Some attributes require boolean values (TRUE or FALSE). These can be
+specified as `true` and `false`. If an attribute has no value assigned
+it gets the default boolean value of true.
+
+## Examples
+```smarty
+{include file="header.tpl"}
+
+{include file="header.tpl" nocache}  // is equivalent to nocache=true
+
+{include file="header.tpl" attrib_name="attrib value"}
+
+{include file=$includeFile}
+
+{include file=#includeFile# title="My Title"}
+
+{assign var=foo value={counter}}  // plugin result
+
+{assign var=foo value=substr($bar,2,5)}  // PHP function result
+
+{assign var=foo value=$bar|strlen}  // using modifier
+
+{assign var=foo value=$buh+$bar|strlen}  // more complex expression
+
+{html_select_date display_days=true}
+
+{mailto address="smarty@example.com"}
+
+<select name="company_id">
+  {html_options options=$companies selected=$company_id}
+</select>
+```
+      
+> **Note**
+>
+> Although Smarty can handle some very complex expressions and syntax,
+> it is a good rule of thumb to keep the template syntax minimal and
+> focused on presentation. If you find your template syntax getting too
+> complex, it may be a good idea to move the bits that do not deal
+> explicitly with presentation to PHP by way of plugins or modifiers.