perf(font): 优化字体渲染并添加抗锯齿设置

- 在所有字体文件中添加 keep_rounding_remainders 属性，提高字体渲染质量
- 更新项目设置，启用抗锯齿功能
- 调整场景文件中的资源引用，添加 UID 信息

engine/scenes/loading/loading.tscn

@@ -1,7 +1,7 @@
 [gd_scene load_steps=5 format=3 uid="uid://cbih1sy4phrk2"]
 
 [ext_resource type="Texture2D" uid="uid://803gf4kme28" path="res://assets/loading/loading_background.png" id="1_76lh6"]
-[ext_resource type="Script" path="res://scripts/loading/loading.gd" id="1_mv03x"]
+[ext_resource type="Script" uid="uid://cqkwp5wocqdx7" path="res://scripts/loading/loading.gd" id="1_mv03x"]
 [ext_resource type="Texture2D" uid="uid://b7nbbjtwrswvu" path="res://assets/loading/progress_background.png" id="2_56muk"]
 [ext_resource type="Texture2D" uid="uid://bay2jnwvmp18d" path="res://assets/loading/progress.png" id="3_106wh"]