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/components/layout/SettingsLayout.tsx

@@ -2,7 +2,7 @@ import React from 'react';
 import {
   CreditCardIcon, UserIcon, CalendarDaysIcon, BuildingOffice2Icon,
   WrenchScrewdriverIcon, BanknotesIcon, UsersIcon, ShieldCheckIcon,
-  TagIcon, ChatBubbleLeftRightIcon, UserCircleIcon,
+  TagIcon, ChatBubbleLeftRightIcon, UserCircleIcon, UserPlusIcon,
 } from '@heroicons/react/24/outline';
 import PurchaseSubscriptionSidebar from './PurchaseSubscriptionSidebar';
 
@@ -27,6 +27,7 @@ export const SETTINGS_MENU: SettingsMenuItem[] = [
   { key: 'services',     label: 'خدمات',              icon: WrenchScrewdriverIcon,    to: '/admin/clinic-services' },
   { key: 'payment',      label: 'مدیریت پرداخت',      icon: BanknotesIcon,            to: '/admin/my-financial' },
   { key: 'secretary',    label: 'مدیریت منشی',        icon: UsersIcon,                to: '/admin/my-secretaries' },
+  { key: 'staff',        label: 'پرسنل',              icon: UserPlusIcon,             to: '/admin/staff' },
   { key: 'insurance',    label: 'مدیریت بیمه',        icon: ShieldCheckIcon,          to: '/admin/insurance-pricing' },
   { key: 'tags',         label: 'برچسب‌ها',           icon: TagIcon,                  to: '/admin/tags-settings' },
   { key: 'sms',          label: 'پیامک‌ها',           icon: ChatBubbleLeftRightIcon,  to: '/admin/sms-wallet' },