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/NewsEntry.jsx

@@ -0,0 +1,17 @@
+import {useTranslation} from 'react-i18next';
+
+import {cn} from '@/lib/utils';
+import {formatDate} from '../utils/format.js';
+import {newsText, newsTitle} from '../utils/news.js';
+
+export default function NewsEntry({entry, className}) {
+    const {i18n} = useTranslation();
+
+    return (
+        <article className={cn('space-y-1', className)}>
+            <p className="text-xs text-muted-foreground">{formatDate(entry.publishedAt, i18n.language, {dateStyle: 'medium'})}</p>
+            <h3 className="font-semibold">{newsTitle(entry, i18n.language)}</h3>
+            <p className="whitespace-pre-line break-words text-sm">{newsText(entry, i18n.language)}</p>
+        </article>
+    );
+}