feat(角色): 添加熊boss的新攻击方式和音效

添加熊boss的四种攻击方式：
1. 箭雨攻击(ArrowSeven)
2. 太阳舞攻击(SunDance)
3. 永恒彩虹攻击(ForeverRainbow)
4. 冲刺攻击(BearSprint)

新增对应攻击音效资源
调整子弹追踪和伤害计算逻辑
添加冲刺粒子特效

scripts/Contents/Bullets/BossAttack/Bear/ArrowSeven.gd

@@ -27,10 +27,10 @@ func ai():
 	if timeLived() <= forwardTime:
 		speed = 10 * ((forwardTime - timeLived()) / forwardTime)
 	elif forwarded:
-		if timeLived() < forwardTime + 1000:
+		if timeLived() < forwardTime + 2000:
 			speed = clamp((timeLived() - forwardTime) / 75, 0, 30)
 			if is_instance_valid(tracer):
-				PresetBulletAI.trace(self, tracer.position, 0.1)
+				PresetBulletAI.trace(self, tracer.position, 0.03)
 	else:
 		forwarded = true