feat(build): migrate to declarative Gradle plugin DSL and bump Dart SDK constraint to >=3.0.0 <4.0.0

android/settings.gradle

@@ -1,11 +1,30 @@
-include ':app'
+pluginManagement {
+    def flutterSdkPath = {
+        def properties = new Properties()
+        def localPropertiesFile = file("local.properties")
+        if (localPropertiesFile.exists()) {
+            localPropertiesFile.withInputStream { properties.load(it) }
+        }
+        def flutterSdkPath = properties.getProperty("flutter.sdk") ?: System.getenv('FLUTTER_ROOT') ?: System.getenv('FLUTTER_HOME')
+        assert flutterSdkPath != null, "flutter.sdk not set in local.properties or FLUTTER_ROOT environment variable"
+        return flutterSdkPath
+    }
+    settings.ext.flutterSdkPath = flutterSdkPath()
 
-def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
-def properties = new Properties()
+    includeBuild("${settings.ext.flutterSdkPath}/packages/flutter_tools/gradle")
 
-assert localPropertiesFile.exists()
-localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
 
-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"
+plugins {
+    id "dev.flutter.flutter-plugin-loader" version "1.0.0"
+    id "com.android.application" version "8.5.2" apply false
+    id "org.jetbrains.kotlin.android" version "1.9.22" apply false
+    id "com.google.gms.google-services" version "4.4.1" apply false
+}
+
+include ":app"