fix(ui): 调整UI元素的边框内边距并新增背景预制体

1.  调整ui6.plist中多个Sprite组件的border边框参数，修正显示排版
2.  新增boghbg背景预制体文件及其元数据配置

assets/resources/gui/auie/boghbg.prefab.meta

@@ -0,0 +1,13 @@
+{
+  "ver": "1.1.50",
+  "importer": "prefab",
+  "imported": true,
+  "uuid": "56a982e0-00ae-4ea4-a412-b54666d0e78b",
+  "files": [
+    ".json"
+  ],
+  "subMetas": {},
+  "userData": {
+    "syncNodeName": "boghbg"
+  }
+}