feat(游戏): 新增背景音乐资源，添加播放逻辑并优化教程UI

新增主页与战斗场景的背景音乐文件及对应的导入配置
在主页和战斗任务组件中添加循环播放背景音乐的逻辑
调整四个新手教程引导预制体的文字、字体、描边与布局参数

assets/resources/gui/element/guide2.prefab

@@ -406,7 +406,7 @@
     "_lpos": {
       "__type__": "cc.Vec3",
       "x": 0,
-      "y": 279.527,
+      "y": 418.633,
       "z": 0
     },
     "_lrot": {
@@ -707,13 +707,13 @@
       "b": 255,
       "a": 255
     },
-    "_string": "点击开始游戏",
+    "_string": "选择一个战斗技能",
     "_horizontalAlign": 1,
     "_verticalAlign": 1,
-    "_actualFontSize": 36,
-    "_fontSize": 35,
+    "_actualFontSize": 46,
+    "_fontSize": 45,
     "_fontFamily": "Arial",
-    "_lineHeight": 40,
+    "_lineHeight": 50,
     "_overflow": 2,
     "_enableWrapText": true,
     "_font": null,
@@ -732,7 +732,7 @@
       "b": 0,
       "a": 255
     },
-    "_outlineWidth": 2,
+    "_outlineWidth": 3,
     "_enableShadow": false,
     "_shadowColor": {
       "__type__": "cc.Color",
@@ -762,8 +762,6 @@
       "__id__": 0
     },
     "fileId": "25KvUjWTBKZq5B20vwtseT",
-    "instance": null,
-    "targetOverrides": null,
     "nestedPrefabInstanceRoots": null
   },
   {
@@ -1178,14 +1176,14 @@
     "__prefab": {
       "__id__": 49
     },
-    "_alignFlags": 40,
+    "_alignFlags": 42,
     "_target": null,
     "_left": 0,
     "_right": 0,
     "_top": 590,
     "_bottom": 590,
     "_horizontalCenter": 0,
-    "_verticalCenter": 0,
+    "_verticalCenter": 418.633,
     "_isAbsLeft": true,
     "_isAbsRight": true,
     "_isAbsTop": true,