fix(helpdesk): address code review findings for Risk Radar

- CR-001/002: Replace hardcoded 'critical', 'Ticket', 'Status' with
  i18n data-label attributes
- CR-004: Add tabindex, role=button, keydown handler to risk cards
  for keyboard accessibility
- CR-005: Add aria-labelledby on detail dialog

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

modules/helpdesk/pages/helpdesk/risk-radar/index(default).phtml

@@ -32,6 +32,10 @@ $periodLabels = [
      data-label-overdue="<?php e(t('overdue')); ?>"
      data-label-net="<?php e(t('net')); ?>"
      data-label-search="<?php e(t('Search customers...')); ?>"
+     data-label-critical="<?php e(t('critical')); ?>"
+     data-label-ticket="<?php e(t('Ticket')); ?>"
+     data-label-status="<?php e(t('Status')); ?>"
+     data-label-age="<?php e(t('Age')); ?>"
      data-label-tickets="<?php e(t('Tickets')); ?>"
      data-label-score="<?php e(t('Risk score')); ?>"
 >
@@ -114,7 +118,7 @@ $periodLabels = [
         <div id="radar-cards" class="helpdesk-risk-radar-grid"></div>
       </div>
 
-      <dialog id="radar-detail-dialog" class="app-dialog-lg">
+      <dialog id="radar-detail-dialog" class="app-dialog-lg" aria-labelledby="radar-detail-title">
         <div class="app-dialog-header">
           <h2 id="radar-detail-title"></h2>
           <button type="button" class="app-dialog-close" aria-label="<?php e(t('Close')); ?>">&times;</button>