feat: implement BackButton component for consistent navigation

- Added BackButton component to standardize back navigation across pages.
- Integrated BackButton into various pages, replacing custom back buttons for consistency.
- Updated PageHeader to accept backTo prop for displaying BackButton when navigating from subpages.
- Created useGoBack hook to handle navigation logic, determining whether to go back in history or redirect to a fallback page.
- Added tests for BackButton and its integration with PageHeader to ensure expected behavior.

assets/admin/pages/AppointmentCreatePage.tsx

@@ -14,6 +14,7 @@ import { WalletChargeLink } from '../components/AppointmentActions';
 import { useDoctorBookingServices } from '../hooks/useDoctorBookingServices';
 import ServiceSlotPicker from '../components/appointments/ServiceSlotPicker';
 import { tehranWallClockToUnix, rialToToman, tomanToRial } from '../lib/utils';
+import BackButton from '../components/ui/BackButton';
 import { digitsOnly, todayIso } from '../lib/utils';
 
 /**
@@ -166,9 +167,7 @@ export default function AppointmentCreatePage() {
     <div style={{ padding: '20px 24px', maxWidth: 1080, margin: '0 auto' }}>
       {/* بردکرامب */}
       <div style={{ display: 'flex', alignItems: 'center', gap: 8, marginBottom: 18 }}>
-        <button onClick={() => navigate(-1)} className="btn sm" style={{ display: 'flex', alignItems: 'center', gap: 4 }}>
-          <ChevronRightIcon style={{ width: 15, height: 15 }} /> بازگشت
-        </button>
+        <BackButton fallback="/admin/appointments" />
         <span style={{ fontSize: 13, color: 'var(--text-3)' }}>نوبت ها</span>
         <span style={{ color: 'var(--text-3)' }}>›</span>
         <span style={{ fontSize: 15, fontWeight: 700, color: 'var(--text)' }}>ثبت نوبت جدید</span>