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

components/Scenes/UI.tscn

@@ -118,3 +118,18 @@ text = "100.0"
 unique_name_in_owner = true
 custom_minimum_size = Vector2(0, 5)
 layout_mode = 2
+
+[node name="itemCollect" type="VBoxContainer" parent="root"]
+unique_name_in_owner = true
+layout_mode = 1
+anchors_preset = -1
+anchor_left = 0.05
+anchor_top = 0.85
+anchor_right = 0.15
+anchor_bottom = 0.95
+offset_left = 0.399998
+offset_top = 45.2
+offset_right = -80.8
+offset_bottom = 0.400024
+grow_vertical = 0
+theme_override_constants/separation = 10