feat(game): 添加全套音效系统（背景BGM+7种攻击音+波次/Boss/死亡/建塔音效），纯Web Audio API合成

game/towers/TowerBase.ts

@@ -2,6 +2,7 @@ import type Phaser from 'phaser'
 import { GameManager } from '../GameManager'
 import { HUD_HEIGHT, COFFEE_COST, STAMINA_MAX, STAMINA_REGEN } from '../constants'
 import { getCellSize } from '../mapRenderer'
+import { AudioEngine } from '../AudioEngine'
 import type { EnemyBase } from '../enemies/EnemyBase'
 
 export abstract class TowerBase {
@@ -141,6 +142,8 @@ export abstract class TowerBase {
       this.isActive = true
       this.imageSprite.setAlpha(1)
       this.updateStaminaBar()
+      // 购买咖啡音效
+      AudioEngine.getInstance().playDingTalk()
       return true
     }
     return false