feat(helpdesk): add empty Dashboard page with sidebar nav item

Adds helpdesk/dashboard route, empty page/view, Overview nav group in the
sidebar, and Dashboard i18n keys (de + en). No content yet.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/helpdesk/pages/helpdesk/dashboard/index().php

@@ -0,0 +1,16 @@
+<?php
+
+use MintyPHP\Buffer;
+use MintyPHP\Module\Helpdesk\HelpdeskAuthorizationPolicy;
+use MintyPHP\Support\Guard;
+
+Guard::requireLogin();
+Guard::requireAbilityOrForbidden(HelpdeskAuthorizationPolicy::ABILITY_ACCESS);
+
+Buffer::set('title', t('Dashboard'));
+Buffer::set('style_groups', json_encode(['helpdesk']));
+$breadcrumbs = [
+    ['label' => t('Home'), 'path' => 'admin'],
+    ['label' => t('Helpdesk'), 'path' => 'helpdesk'],
+    ['label' => t('Dashboard')],
+];

modules/helpdesk/pages/helpdesk/dashboard/index(default).phtml

@@ -0,0 +1,8 @@
+<div class="app-details-container">
+  <section>
+    <?php
+    $titlebar = ['title' => t('Dashboard')];
+    require templatePath('partials/app-details-titlebar.phtml');
+    ?>
+  </section>
+</div>