feat: hide slug from user

lib/mv_web/live/custom_field_live/show.ex

@@ -50,7 +50,12 @@ defmodule MvWeb.CustomFieldLive.Show do
       <.list>
         <:item title="Id">{@custom_field.id}</:item>
 
-        <:item title="Slug">{@custom_field.slug}</:item>
+        <:item title="Slug">
+          {@custom_field.slug}
+          <p class="mt-2 text-sm leading-6 text-zinc-600">
+            {gettext("Auto-generated identifier (immutable)")}
+          </p>
+        </:item>
 
         <:item title="Name">{@custom_field.name}</:item>