fix(game): 修复底部塔面板不可见问题，改用React层实现，并用AI素材替换Graphics像素块

game/towers/TowerManager.ts

@@ -106,8 +106,8 @@ export class TowerManager {
 
     const hasTarget = enemies.some((e) => {
       if (e.isDead) return false
-      const dx = e.sprite.x - tower['px']
-      const dy = e.sprite.y - tower['py']
+      const dx = e.x - tower['px']
+      const dy = e.y - tower['py']
       return Math.sqrt(dx * dx + dy * dy) <= tower.attackRange * TILE_SIZE
     })