feat: 添加主界面开屏动画

MainActivity首次启动时显示5秒开屏画面，展示应用标题和副标题。

- 使用FrameLayout覆盖层实现居中展示
- 标题和副标题依次淡入，5秒后整体淡出
- 开屏背景使用主色调，文字白色/半透明白色
- onDestroy中清理Handler防止内存泄漏

bytheway/src/main/res/values/strings.xml

@@ -4,5 +4,7 @@
     <string name="action_gps_list">GPS列表</string>
     <string name="action_about">应用介绍</string>
 	<string name="app_description">The [ByTheWay] project is designed to quickly schedule task reminders related to time and location. Its main feature is the ability to quickly create task-related data.</string>
-	
+	<string name="splash_title">ByTheWay</string>
+	<string name="splash_subtitle">By the way, I mention this for you.</string>
+
 </resources>