feat(UI): 添加物品收集显示功能

- 新增CameraManager脚本用于相机管理
- 在UI场景中添加物品收集容器VBoxContainer
- 扩展ItemShow类支持生成物品显示实例
- 修改EntityBase添加物品收集信号和处理逻辑
- 调整BossBar位置和布局属性

scripts/Statemachine/EntityBase.gd

@@ -7,6 +7,8 @@ signal healthChanged(health: float)
 
 signal energyChanged(energy: float)
 
+signal itemCollected(itemType: ItemStore.ItemType, amount: int)
+
 var fields = {
 	FieldStore.Entity.MAX_HEALTH: 100,
 	FieldStore.Entity.DAMAGE_MULTIPILER: 1,
@@ -72,6 +74,7 @@ func _ready():
 				if body is ItemDropped:
 					inventory[body.item] += body.stackCount
 					playSound("collect")
+					itemCollected.emit(body.item, body.stackCount)
 					body.queue_free()
 		)
 		energyChanged.connect(
@@ -79,6 +82,10 @@ func _ready():
 				UIState.energyPercent.maxValue = fields.get(FieldStore.Entity.MAX_ENERGY)
 				UIState.energyPercent.setCurrent(newEnergy)
 		)
+		itemCollected.connect(
+			func(itemType, amount):
+				UIState.itemCollect.add_child(ItemShow.generate(itemType, amount))
+		)
 	else:
 		currentFocusedBoss = get_tree().get_nodes_in_group("players")[0]
 	healthChanged.emit(health)