refactor(SettingsPage): replace PTR zone icon with IconWorld for improved clarity

frontend/src/SettingsPage.jsx

@@ -7,7 +7,7 @@ import {
   IconNetwork,
   IconCloud,
   IconChartPie,
-  IconDns,
+  IconWorld,
   IconChevronDown,
 } from '@tabler/icons-react';
 import FormField from './components/FormField';
@@ -461,7 +461,7 @@ export default function SettingsPage() {
               <SectionCard
                 id="ptr-zone"
                 title="Настройка PTR зоны"
-                icon={IconDns}
+                icon={IconWorld}
                 defaultOpen={true}
               >
                 <div className="row g-3">