fix: preserve aspect ratio for Ludo pawn sprites on canvas

Use Math.min() scaling (same approach as chess pieces) instead of
forcing sprites into a square bounding box which stretched non-square
pawn images uploaded via admin branding.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

public/js/modules/ludo/scenes/game.js

@@ -1115,7 +1115,12 @@ function drawPieces(cs) {
       const pColor = COLORS[bSlot2];
       if (spriteImg) {
         const size = r * 2;
-        ctx.drawImage(spriteImg, ox - size/2, drawY - size/2, size, size);
+        const iw = spriteImg.naturalWidth || spriteImg.width;
+        const ih = spriteImg.naturalHeight || spriteImg.height;
+        const scale = Math.min(size / iw, size / ih);
+        const dw = iw * scale;
+        const dh = ih * scale;
+        ctx.drawImage(spriteImg, ox - dw/2, drawY - dh/2, dw, dh);
       } else {
         ctx.beginPath(); ctx.arc(ox, drawY - r*0.15, r*0.65, 0, Math.PI*2); ctx.fillStyle = pColor; ctx.fill();
         ctx.beginPath(); ctx.ellipse(ox, drawY + r*0.4, r*0.8, r*0.4, 0, 0, Math.PI*2); ctx.fillStyle = pColor; ctx.fill();