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.

public/i18n/en.json

@@ -72,7 +72,9 @@
     "STEAM_GAMES": "Steam Games",
     "NO_STEAM_ID": "No Steam ID saved yet – add it in the settings",
     "MOST_PLAYED": "Most played",
-    "SHOW_ALL": "Show all"
+    "SHOW_ALL": "Show all",
+    "TO_LIBRARY": "Go to library",
+    "WELCOME_BACK": "Welcome back"
   },
   "LIBRARY": {
     "TITLE": "Game Library",
@@ -138,6 +140,10 @@
     "DASHBOARD": "Dashboard",
     "LIBRARY": "Library",
     "SETTINGS": "Settings",
-    "TO_DASHBOARD": "Go to dashboard"
+    "TO_DASHBOARD": "Go to dashboard",
+    "MENU": "Menu",
+    "LANGUAGE": "Language",
+    "DARK_MODE": "Dark mode",
+    "LIGHT_MODE": "Light mode"
   }
 }