UNO refactor (stage 1): hub shell with nav rail + internal-scroll panel

Rebuild ScreenShell into a UNO-style app shell: a persistent NavRail (vertical
side rail in landscape, bottom tab bar in portrait — Home/Profile/Shop/Friends/
Leaderboard/Achievements, active highlighted gold) + a content panel that owns
its own scroll so the page never scrolls as a whole and uses the width in
landscape. Reskins all 10 menu screens at once. Transient screens (auth,
matchmaking, room) opt out via hideNav. New nav.home i18n key.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/lib/i18n.tsx

@@ -108,6 +108,7 @@ const fa: Dict = {
   "speed.desc": "حالت سریع: نوبت‌های کوتاه‌تر و بازی برق‌آسا",
   "menu.online": "بازی آنلاین",
   "menu.onlineDesc": "با دوستان یا بازیکن‌های واقعی",
+  "nav.home": "خانه",
   "menu.profile": "پروفایل",
   "menu.friends": "دوستان",
   "menu.leaderboard": "جدول امتیازات",
@@ -450,6 +451,7 @@ const en: Dict = {
   "speed.desc": "Blitz mode: short turns, lightning-fast match",
   "menu.online": "Play Online",
   "menu.onlineDesc": "With friends or real players",
+  "nav.home": "Home",
   "menu.profile": "Profile",
   "menu.friends": "Friends",
   "menu.leaderboard": "Leaderboard",