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/App.jsx

@@ -9,6 +9,8 @@ import Dashboard from "./pages/Dashboard.jsx";
 import RegistrationPage from './pages/RegistrationPage.jsx';
 import SettingsPage from './pages/SettingsPage.jsx';
 import AdminHintsPage from './pages/AdminHintsPage.jsx';
+import AdminNewsPage from './pages/AdminNewsPage.jsx';
+import WhatsNewPage from './pages/WhatsNewPage.jsx';
 import AdminUsersPage from './pages/AdminUsersPage.jsx';
 import GameLibrary from './pages/GameLibrary.jsx';
 import GameDetail from './pages/GameDetail.jsx';
@@ -71,8 +73,10 @@ function App() {
                             <Route path="/stats" element={<StatsPage/>}/>
                             <Route path="/import" element={<ImportPage/>}/>
                             <Route path="/settings" element={<SettingsPage/>}/>
+                            <Route path="/whats-new" element={<WhatsNewPage/>}/>
                             <Route path="/admin/users" element={<AdminUsersPage/>}/>
                             <Route path="/admin/hints" element={<AdminHintsPage/>}/>
+                            <Route path="/admin/news" element={<AdminNewsPage/>}/>
                         </Route>
                         <Route path="/u/:name" element={<PublicProfilePage/>}/>
                         <Route path="/impressum" element={<ImprintPage/>}/>