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/utils/limits.js

@@ -30,3 +30,6 @@ export const MAX_CORRECTION_GENRES = 10;
 export const MAX_DISPLAY_NAME_LENGTH = 24;
 // Auth CreateHintRequest @Size(max = 500)
 export const MAX_HINT_LENGTH = 500;
+// Auth NewsRequest @Size(max = 100) and @Size(max = 2000)
+export const MAX_NEWS_TITLE_LENGTH = 100;
+export const MAX_NEWS_TEXT_LENGTH = 2000;

src/utils/news.js

@@ -0,0 +1,39 @@
+import {apiFetch} from './api.js';
+
+const AUTH = () => import.meta.env.VITE_API_URL;
+const JSON_HEADERS = {'Content-Type': 'application/json'};
+
+/**
+ * GET /api/news: {results: [{id, titleEn, titleDe, textEn, textDe, publishedAt, seen}]}, every entry, newest first.
+ */
+export const fetchNews = () => apiFetch(`${AUTH()}/api/news`);
+
+/**
+ * All entries published until now count as seen for this user.
+ */
+export const markNewsSeen = () => apiFetch(`${AUTH()}/api/news/seen`, {method: 'PUT'});
+
+/**
+ * PLATFORM_ADMIN only (403 otherwise): {results: [...]}, every entry with createdBy and createdAt, newest first.
+ */
+export const fetchAdminNews = () => apiFetch(`${AUTH()}/api/admin/news`);
+
+/**
+ * 201 {id}, or 400 for a blank English title or text, or a title over 100 or a text over 2000 characters.
+ */
+export const createNews = (news) =>
+    apiFetch(`${AUTH()}/api/admin/news`, {method: 'POST', headers: JSON_HEADERS, body: JSON.stringify(news)});
+
+/**
+ * 204, 404 for an unknown id. The published date stays.
+ */
+export const updateNews = (newsId, news) =>
+    apiFetch(`${AUTH()}/api/admin/news/${newsId}`, {method: 'PUT', headers: JSON_HEADERS, body: JSON.stringify(news)});
+
+export const deleteNews = (newsId) => apiFetch(`${AUTH()}/api/admin/news/${newsId}`, {method: 'DELETE'});
+
+const pick = (de, en, language) => (language?.startsWith('de') && de ? de : en);
+
+export const newsTitle = (entry, language) => pick(entry.titleDe, entry.titleEn, language);
+
+export const newsText = (entry, language) => pick(entry.textDe, entry.textEn, language);