feat: add What's new feature

Dashboard dialog shows unseen news entries. Users mark them seen with "Got it"
or revisit via the /whats-new page. Admins publish, edit, and delete entries
on /admin/news. Full i18n support and test coverage included.

src/components/AppHeader.jsx

@@ -1,7 +1,7 @@
 import {useEffect, useState} from 'react';
 import {Link, NavLink, useLocation, useNavigate} from 'react-router-dom';
 import {useTranslation} from 'react-i18next';
-import {ChartColumn, Dices, Eye, Languages, LayoutDashboard, Library, LogOut, Megaphone, Moon, Settings, Shield, Sun} from 'lucide-react';
+import {ChartColumn, Dices, Eye, Languages, LayoutDashboard, Library, LogOut, Megaphone, Moon, Newspaper, Settings, Shield, Sun} from 'lucide-react';
 import {toast} from 'sonner';
 
 import {Badge} from '@/components/ui/badge';
@@ -144,6 +144,9 @@ export default function AppHeader({isAuthenticated, onLogout}) {
                                 <DropdownMenuItem asChild>
                                     <Link to="/settings"><Settings/>{t('NAV.SETTINGS')}</Link>
                                 </DropdownMenuItem>
+                                <DropdownMenuItem asChild>
+                                    <Link to="/whats-new"><Newspaper/>{t('NAV.WHATS_NEW')}</Link>
+                                </DropdownMenuItem>
                                 {seesAdminPage && (
                                     <>
                                         <DropdownMenuItem asChild>
@@ -155,6 +158,9 @@ export default function AppHeader({isAuthenticated, onLogout}) {
                                         <DropdownMenuItem asChild>
                                             <Link to="/admin/hints"><Megaphone/>{t('NAV.ADMIN_HINTS')}</Link>
                                         </DropdownMenuItem>
+                                        <DropdownMenuItem asChild>
+                                            <Link to="/admin/news"><Newspaper/>{t('NAV.ADMIN_NEWS')}</Link>
+                                        </DropdownMenuItem>
                                     </>
                                 )}
                                 {isAdmin && (