fix: 修复欢迎板和通知板通知无法关闭问题

- 修复欢迎板和通知板当前被ChatUI 抢占鼠标问题，通过设置启动弹窗时ChatUI 根节点 mouse_filter 临时改为 IGNORE来实现
- ToDo: 后续统一规划事件逻辑

scenes/prefabs/items/welcome_board.tscn

@@ -1,6 +1,5 @@
-[gd_scene load_steps=4 format=3 uid="uid://c7k8yay002w4"]
+[gd_scene load_steps=3 format=3 uid="uid://c7k8yay002w4"]
 
-[ext_resource type="Script" uid="uid://d2od22agputjt" path="res://scenes/prefabs/items/WelcomeBoard.gd" id="1_script"]
 [ext_resource type="Texture2D" uid="uid://v7loa3smfkrd" path="res://assets/materials/WelcomeBoard.png" id="2_sprite"]
 
 [sub_resource type="RectangleShape2D" id="RectangleShape2D_board"]
@@ -8,7 +7,6 @@ size = Vector2(112, 26.5)
 
 [node name="WelcomeBoard" type="StaticBody2D"]
 collision_layer = 3
-script = ExtResource("1_script")
 
 [node name="Sprite2D" type="Sprite2D" parent="."]
 scale = Vector2(0.25, 0.25)