fix: backgammon board LANDSCAPE — width-driven, aspect-ratio 1.45:1

Real backgammon boards are wider than tall. Board now uses width:100%
with aspect-ratio 1.45/1, expanding to fill available horizontal space.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

public/css/backgammon.css

@@ -38,18 +38,16 @@
     flex-direction: column;
     gap: 4px;
     align-items: center;
-    justify-content: center;
     flex: 1;
     min-width: 0;
+    max-width: 900px;
 }
 
 /* ─── Board Frame ────────────────────────────────────────────────────────── */
 .bg-board {
     position: relative;
-    height: min(calc(100vh - 160px), 680px);
-    aspect-ratio: 1.35 / 1;
-    width: auto;
-    max-width: 100%;
+    width: 100%;
+    aspect-ratio: 1.45 / 1;
     background: var(--bg-board-wood);
     border-width: 10px;
     border-style: solid;
@@ -997,8 +995,8 @@
 
 /* ─── Responsive: Large screens ──────────────────────────────────────────── */
 @media (min-width: 1024px) {
-    .bg-board {
-        height: min(calc(100vh - 140px), 740px);
+    .bg-board-column {
+        max-width: 1000px;
     }
 
     :root {