Refactor API structure: add internal handling, update templates, and remove deprecated files

api/setup/save.php

@@ -80,7 +80,8 @@ $settings = [
     "application_name" => "Guestbook",
     "allow_html" => "false",
     "approve_entrys" => "true",
-    "allow_new_entrys" => "true"
+    "allow_new_entrys" => "true",
+    "template" => "standard"
 ];
 
 foreach ($settings as $key => $value) {