feat(nav): merge Random Mix & Albums into Build a Mix hub

Replaces two sidebar entries (Random Mix, Random Albums) with a single 'Build a Mix' item (Wand2 icon) at /random. Landing page shows two cards — Mix by Tracks and Mix by Albums — with glow-on-hover. Old routes updated throughout. All 7 locales updated.

src/pages/Home.tsx

@@ -120,7 +120,7 @@ export default function Home() {
             {isVisible('discover') && (
               <AlbumRow
                 title={t('home.discover')}
-                titleLink="/random-albums"
+                titleLink="/random/albums"
                 albums={random}
                 onLoadMore={() => loadMore('random', random, setRandom)}
                 moreText={t('home.discoverMore')}