refactor: move secretary and staff management from main nav to settings menu

Remove پرسنل (/admin/staff) and منشی ها (/admin/my-secretaries) from the
clinic and doctor main sidebars; surface them under the settings menu instead
(PurchaseSubscriptionSidebar + SETTINGS_MENU). Wrap StaffPage in SettingsLayout
so it renders inside the settings shell like MySecretariesPage already does.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

assets/admin/pages/StaffPage.tsx

@@ -13,6 +13,7 @@ import DataTable, { type Column } from '../components/ui/DataTable';
 import Modal from '../components/ui/Modal';
 import ConfirmDialog from '../components/ui/ConfirmDialog';
 import PageHeader from '../components/ui/PageHeader';
+import SettingsLayout from '../components/layout/SettingsLayout';
 import { ActiveBadge } from '../components/ui/StatusBadge';
 
 const schema = z.object({
@@ -155,7 +156,7 @@ export default function StaffPage() {
   ];
 
   return (
-    <>
+    <SettingsLayout active="staff">
       <PageHeader
         title="مدیریت پرسنل"
         description="لیست پرسنل کلینیک / مطب"
@@ -239,7 +240,7 @@ export default function StaffPage() {
         onCancel={() => setToggleTarget(null)}
         loading={toggleMutation.isPending}
       />
-    </>
+    </SettingsLayout>
   );
 }