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/components/ui/PageHeader.tsx

@@ -1,6 +1,7 @@
 import React from 'react';
 import { Link } from 'react-router-dom';
 import { ChevronLeftIcon } from '@heroicons/react/24/outline';
+import BackButton from './BackButton';
 
 interface Crumb {
   label: string;
@@ -12,12 +13,22 @@ interface Props {
   breadcrumbs?: Crumb[];
   action?: React.ReactNode;
   description?: string;
+  /**
+   * صفحه از دل صفحهٔ دیگری باز می‌شود → دکمهٔ «بازگشت» بالای عنوان.
+   * مقدار، مقصدِ fallback است وقتی تاریخچه‌ای برای برگشتن نیست.
+   */
+  backTo?: string;
 }
 
-export default function PageHeader({ title, breadcrumbs, action, description }: Props) {
+export default function PageHeader({ title, breadcrumbs, action, description, backTo }: Props) {
   return (
     <div style={{ display: 'flex', alignItems: 'flex-start', justifyContent: 'space-between', gap: 16, marginBottom: 24 }}>
       <div style={{ minWidth: 0 }}>
+        {backTo && (
+          <div style={{ marginBottom: 10 }}>
+            <BackButton fallback={backTo} />
+          </div>
+        )}
         {breadcrumbs && breadcrumbs.length > 0 && (
           <nav style={{ display: 'flex', alignItems: 'center', gap: 4, marginBottom: 6, fontSize: 12, color: 'var(--text-3)' }}>
             {breadcrumbs.map((crumb, i) => (