feat(i18n): add English localization with per-user language preference

app/templates/admin_invites.html

@@ -93,7 +93,7 @@
 {% else %}
 <div class="empty-state">
     <div class="empty-icon">🔑</div>
-    <p>{{ 'invites.title'|t(user.language) }}</p>
+    <p>{{ 'invites.empty'|t(user.language) }}</p>
 </div>
 {% endif %}