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-merge-compiled-includes.md

@@ -0,0 +1,27 @@
+\$merge\_compiled\_includes {#variable.merge.compiled.includes}
+===========================
+
+By setting `$merge_compiled_includes` to TRUE Smarty will merge the
+compiled template code of subtemplates into the compiled code of the
+main template. This increases rendering speed of templates using a many
+different sub-templates.
+
+Individual sub-templates can be merged by setting the `inline` option
+flag within the `{include}` tag. `$merge_compiled_includes` does not
+have to be enabled for the `inline` merge.
+
+::: {.informalexample}
+
+    <?php
+    $smarty->merge_compiled_includes = true;
+    ?>
+
+            
+:::
+
+> **Note**
+>
+> This is a compile time option. If you change the setting you must make
+> sure that the templates get recompiled.
+
+See also [`{include}`](#language.function.include) tag