Panel admina: 16 zakladek jako podsciezki /admin/*

- aktywna zakladka wyznaczana z adresu (useParams), nie z useState
- setTab() nawiguje zamiast zmieniac stan lokalny
- sidebar admina: <button> -> <NavLink>
- typ AdminTab zunifikowany z AdminTabKey z routes.ts
- nieznana sekcja /admin/cokolwiek -> strona 404
- CSS .admin-nav rozszerzony o warianty <a>

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/App.tsx

@@ -3665,10 +3665,8 @@ function accountStorageKey(suffix: string, user: AuthUser | null): string {
   return `accountProfile:${user?.id ?? 'guest'}:${suffix}`;
 }
 
-type AdminTab =
-  | 'dashboard' | 'listings' | 'users' | 'messages' | 'reports' | 'payments'
-  | 'stats' | 'settings' | 'moderation' | 'categories' | 'locations' | 'promotions' | 'forbiddenWords'
-  | 'leads' | 'campaigns' | 'mailConfig';
+// Zakladki panelu maja odpowiedniki w sciezkach /admin/* - jedno zrodlo prawdy w routes.ts.
+type AdminTab = AdminTabKey;
 
 const ADMIN_TAB_META: Record<AdminTab, { title: string; subtitle: string }> = {
   dashboard: { title: 'Panel administratora', subtitle: 'Zarządzaj ogłoszeniami i użytkownikami serwisu.' },
@@ -3848,7 +3846,14 @@ function AdminMessageModal({ user, onClose }: { user: AuthUser; onClose: () => v
 function AdminPage() {
   const navigate = useNavigate();
   const { user } = useAuth();
-  const [tab, setTab] = useState<AdminTab>('dashboard');
+  // Aktywna zakladka wynika z adresu (/admin/leady), nie ze stanu komponentu -
+  // dzieki temu kazda sekcja panelu ma wlasny URL, dziala F5 i przycisk Wstecz.
+  const adminSegment = useParams()['*'] ?? '';
+  const tab: AdminTab = ADMIN_PATH_TO_TAB[adminSegment] ?? 'dashboard';
+  const isUnknownAdminSection = adminSegment !== '' && !(adminSegment in ADMIN_PATH_TO_TAB);
+  const setTab = useCallback((next: AdminTab) => {
+    navigate(adminTabPath(next));
+  }, [navigate]);
   const [users, setUsers] = useState<AuthUser[]>([]);
   const [listings, setListings] = useState<AdminListing[]>([]);
   const [reports, setReports] = useState<AdminListingReport[]>([]);
@@ -4193,6 +4198,10 @@ function AdminPage() {
     }
   };
 
+  if (isUnknownAdminSection) {
+    return <NotFoundPage />;
+  }
+
   return (
     <section className="admin-page admin-page-shell" aria-label="Panel administratora">
       <div className="admin-shell admin-shell-with-sidebar">
@@ -4201,31 +4210,26 @@ function AdminPage() {
 
           <nav className="admin-nav">
             {ADMIN_NAV_ITEMS.map((item) => (
-              <button
+              <NavLink
                 key={item.id}
-                type="button"
-                className={tab === item.id ? 'active' : ''}
-                onClick={() => setTab(item.id)}
+                to={adminTabPath(item.id)}
+                end={item.id === 'dashboard'}
+                className={navLinkClass}
               >
                 <Icon name={item.icon} /> {item.label}
                 {item.id === 'listings' && pendingCount > 0 && <b>{pendingCount}</b>}
                 {item.id === 'users' && pendingVerificationCount > 0 && <b>{pendingVerificationCount}</b>}
                 {item.id === 'reports' && pendingReportsCount > 0 && <b>{pendingReportsCount}</b>}
-              </button>
+              </NavLink>
             ))}
           </nav>
 
           <p className="admin-nav-group-label">Narzędzia</p>
           <nav className="admin-nav">
             {ADMIN_TOOL_ITEMS.map((item) => (
-              <button
-                key={item.id}
-                type="button"
-                className={tab === item.id ? 'active' : ''}
-                onClick={() => setTab(item.id)}
-              >
+              <NavLink key={item.id} to={adminTabPath(item.id)} className={navLinkClass}>
                 <Icon name={item.icon} /> {item.label}
-              </button>
+              </NavLink>
             ))}
           </nav>