fix: chess board ACTUALLY visible now

Two problems:
1. --board-light and --board-dark CSS vars were in deleted app.css
   → Added all chess board CSS vars to el3ab.css :root

2. .board-wrapper layout broken in our flex context
   → Added explicit override: aspect-ratio:1, position:relative
   → Kill the ::before padding hack (use aspect-ratio)
   → Force .board to position:absolute;inset:0;width:100%;height:100%
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/styles/el3ab.css

@@ -45,6 +45,28 @@
   --font: 'IBM Plex Sans Arabic', system-ui, sans-serif;
   --ease: cubic-bezier(0.2, 0, 0, 1);
   --ease-bounce: cubic-bezier(0.34, 1.56, 0.64, 1);
+
+  /* Chess board colors (needed by chessboard.css) */
+  --board-light: #EBECD0;
+  --board-dark: #779556;
+  --board-selected: rgba(255, 255, 50, 0.5);
+  --board-legal: rgba(0, 0, 0, 0.15);
+  --board-last-move: rgba(255, 255, 50, 0.4);
+  --board-check: rgba(255, 0, 0, 0.6);
+  --board-premove: rgba(21, 180, 240, 0.3);
+  --board-highlight-green: rgba(21, 180, 90, 0.4);
+  --board-highlight-red: rgba(220, 50, 50, 0.4);
+  --board-highlight-yellow: rgba(220, 180, 30, 0.4);
+
+  /* Other vars chessboard.css references */
+  --bg-3: #182B42;
+  --text-inverse: #0F172A;
+  --border: rgba(255, 255, 255, 0.08);
+  --radius-md: 12px;
+  --radius-sm: 8px;
+  --font-en: 'Inter', system-ui, sans-serif;
+  --error: #EF4444;
+  --eval-label-light: #fff;
 }
 
 *, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
@@ -288,7 +310,24 @@ img { display: block; max-width: 100%; }
 }
 
 /* === RESPONSIVE GAME BOARD === */
-/* board-wrapper is styled in chessboard.css — we just constrain its width inline */
+/* Override chessboard.css board-wrapper to work in our layout */
+.chess-game-wrap .board-wrapper {
+  position: relative;
+  width: min(calc(100vw - 24px), 400px) !important;
+  aspect-ratio: 1;
+  margin: 0 auto;
+  flex: none !important;
+}
+.chess-game-wrap .board-wrapper::before {
+  display: none !important; /* Kill the padding-top hack, use aspect-ratio instead */
+}
+.chess-game-wrap .board-wrapper > .board,
+.chess-game-wrap .board-wrapper > #board {
+  position: absolute !important;
+  inset: 0 !important;
+  width: 100% !important;
+  height: 100% !important;
+}
 
 /* === MATCHMAKING RADAR === */
 .matchmaking-radar {