feat(子弹系统): 重构伤害计算并添加音效

将子弹的伤害属性从`damage`重命名为`baseDamage`，并引入`damageMultipliers`数组支持多段伤害
为火山武器添加三段攻击音效并调整伤害倍率
更新相关武器和子弹脚本以适配新的伤害系统

scripts/Contents/Weapons/MushroomPickaxe.gd

@@ -10,7 +10,7 @@ func attack(entity: EntityBase):
 	var weaponPos = entity.findWeaponAnchor("normal")
 	for j in BulletBase.generate(ComponentManager.getBullet("MushroomPickaxe"), entity, entity.texture.global_position, weaponPos.angle_to_point(get_global_mouse_position())):
 		var bullet: MushroomPickaxe = j
-		bullet.damage = readStore("atk")
+		bullet.baseDamage = readStore("atk")
 		bullet.rate = readStore("rate")
 		bullet.count = readStore("count")
 	return true