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/PatientRecordFormPage.tsx

@@ -12,6 +12,7 @@ import type { PatientRecord } from '../types';
 import PersianDateInput from '../components/ui/PersianDateInput';
 import SearchableSelect from '../components/ui/SearchableSelect';
 import { numericField } from '../lib/forms';
+import BackButton from '../components/ui/BackButton';
 import { iranNationalCodeSchema, iranMobileSchema, unixToIso } from '../lib/utils';
 
 const REFERRAL_OPTIONS = ['اینستاگرام', 'معرفی دوستان و آشنایان', 'جستجوی اینترنتی', 'تابلو مطب', 'سایر'];
@@ -105,7 +106,7 @@ export default function PatientRecordFormPage() {
   return (
     <div className="fade-in" style={{ maxWidth: 1000, margin: '0 auto' }}>
       <div style={{ display: 'flex', alignItems: 'center', gap: 10, marginBottom: 18 }}>
-        <Link to="/admin/patients" className="btn sm ghost" style={{ color: 'var(--text-2)' }}><ChevronRightIcon style={{ width: 16 }} /> بازگشت</Link>
+        <BackButton fallback="/admin/patients" />
         <div style={{ fontSize: 14, color: 'var(--text-3)' }}>پرونده › <b style={{ color: 'var(--text)' }}>{isEdit ? 'ویرایش پرونده' : 'تشکیل پرونده'}</b></div>
       </div>