feat(app): integrate SplashScreen and reportFullyDrawn in MainActivity

app/src/main/kotlin/plus/rua/project/MainActivity.kt

@@ -2,15 +2,20 @@ package plus.rua.project
 
 import android.content.Intent
 import android.os.Bundle
+import androidx.activity.compose.ReportDrawn
 import androidx.activity.compose.setContent
+import androidx.core.splashscreen.SplashScreen.Companion.installSplashScreen
 import plus.rua.project.ui.CalendarMonthView
 import plus.rua.project.ui.theme.YaYaTheme
 
 class MainActivity : BaseActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
+        installSplashScreen()
         super.onCreate(savedInstanceState)
 
         setContent {
+            // 在首次 composition 绘制完成后报告 fully drawn，用于准确的启动时间度量。
+            ReportDrawn()
             YaYaTheme {
                 CalendarMonthView(
                     onNavigateToAbout = {