refactor(2048): simplify tile text colors to white on all dark-themed tiles

Previously, tile text colors alternated between dark (#1a1208) for lower
values and white (#ffffff) for higher values (index >= 5). This change
simplifies the logic to use white text for all tiles, reflecting a
consistent dark-themed tile design.

src/games/2048/2048Logic.js

@@ -29,9 +29,9 @@ export function buildTilePalette(scheme) {
   return palette;
 }
 
-// Returns 11 hex color strings for tile text (light on dark, dark on light)
+// Returns 11 hex color strings for tile text — white on all dark-themed tiles
 export function buildTextColorTable(palette) {
-  return palette.map((_, i) => (i >= 5 ? '#ffffff' : '#1a1208'));
+  return palette.map(() => '#ffffff');
 }
 
 // Map tile value (2..2048+) to palette index 0-10