Landscape: whole-app landscape-first + Home 2-column landscape layout

- Move orientation lock + RotatePrompt to app root → whole app is landscape-
  first now (UNO-style), not just the game. Generalized rotate copy.
- Home: portrait unchanged; in landscape it becomes a 2-column app layout
  (col A = branding + play actions, col B = tiles + footer) that fits the
  short height with no scroll (landscape: Tailwind variants, overflow-hidden).

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

src/app/page.tsx

@@ -22,6 +22,7 @@ import { ResumeGameBar } from "@/components/online/ResumeGameBar";
 import { CelebrationOverlay } from "@/components/online/CelebrationOverlay";
 import { ErrorBoundary } from "@/components/ErrorBoundary";
 import { PublicProfileModal } from "@/components/online/PublicProfileModal";
+import { RotatePrompt } from "@/components/online/RotatePrompt";
 import { CapacitorBack } from "@/components/CapacitorBack";
 import { useSessionStore } from "@/lib/session-store";
 import { useGameStore } from "@/lib/game-store";
@@ -191,6 +192,14 @@ export default function Page() {
     };
   }, [init]);
 
+  // Landscape-first app (UNO-style): best-effort lock the whole app to landscape
+  // on Android / installed PWA. iOS & desktop reject it harmlessly; the
+  // RotatePrompt covers the portrait case there.
+  useEffect(() => {
+    const o = (screen as unknown as { orientation?: { lock?: (m: string) => Promise<void> } }).orientation;
+    o?.lock?.("landscape").catch(() => {});
+  }, []);
+
   return (
     // reducedMotion="user" makes every Framer Motion animation honor the OS
     // "reduce motion" accessibility setting (coin rain, confetti, count-ups…).
@@ -202,6 +211,7 @@ export default function Page() {
         <ResumeGameBar />
         <CelebrationOverlay />
         <PublicProfileModal />
+        <RotatePrompt />
       </ErrorBoundary>
       <CapacitorBack />
       {loading && null}