feat(ui): modern shadcn/ui theme with violet accent across all pages

Add shadcn/ui (Radix + Tailwind 4) components, zinc/violet theme tokens and self-hosted Inter. New header with user menu, Steam cover art, skeletons and toasts. Replace @mdi/font with lucide-react. Fix: top-owned list on the landing page only showed with top-played entries; numbers use the app language.

src/utils/games.js

@@ -9,3 +9,6 @@ export const formatPlaytime = (minutes) => {
     const hours = Math.round(minutes / 6) / 10;
     return hours >= 10 ? `${Math.round(hours)}h` : `${hours.toFixed(1)}h`;
 };
+
+// 460x215 store header. Not every app has one; callers need an onError fallback.
+export const coverUrl = (appid) => `https://cdn.cloudflare.steamstatic.com/steam/apps/${appid}/header.jpg`;