feat: upgrade Flutter version to 3.38 (#1256)

ui/flutter/android/settings.gradle

@@ -1,11 +1,25 @@
+pluginManagement {
+    def flutterSdkPath = {
+        def properties = new Properties()
+        file('local.properties').withInputStream { properties.load(it) }
+        def flutterSdkPath = properties.getProperty('flutter.sdk')
+        assert flutterSdkPath != null, 'flutter.sdk not set in local.properties'
+        return flutterSdkPath
+    }()
+
+    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
+
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+
+plugins {
+    id 'dev.flutter.flutter-plugin-loader' version '1.0.0'
+    id 'com.android.application' version '8.7.3' apply false
+    id 'org.jetbrains.kotlin.android' version '2.1.0' apply false
+}
+
 include ':app'
-
-def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
-def properties = new Properties()
-
-assert localPropertiesFile.exists()
-localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
-
-def flutterSdkPath = properties.getProperty("flutter.sdk")
-assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
-apply from: "$flutterSdkPath/packages/flutter_tools/gradle/app_plugin_loader.gradle"