Compatibility issue with Gradle 9+ / AGP 9+

**Flutter support for your project's Android Gradle Plugin version (Android Gradle Plugin version 8.12.1) will soon be dropped. Please upgrade your Android Gradle Plugin version to a version of at least Android Gradle Plugin version 9.0.1 soon.**

flutter_downloader currently prevents upgrading a Flutter project to the latest Android Gradle Plugin / Gradle versions.

My Flutter project requires AGP 9+ / Gradle 9+, but the Android configuration of flutter_downloader is not compatible with the newer Gradle/AGP setup.

Because flutter_downloader is included as a dependency, the project cannot be upgraded successfully without modifying the plugin.

Expected behavior

flutter_downloader should support current Flutter Android projects using:

Android Gradle Plugin: 9+
Gradle: 9+
Java: 17+
Current stable Flutter versions

The plugin should build successfully without requiring the application to downgrade its Android Gradle Plugin or Gradle version.

Actual behavior

When upgrading the project to the newer Gradle/AGP version, the build fails because flutter_downloader is not compatible with the new Android build configuration.

This effectively prevents applications using flutter_downloader from upgrading their Android build tooling.

Impact

This is blocking our project from upgrading to the latest Flutter Android build configuration.

We would appreciate an update to flutter_downloader to support AGP 9.x / Gradle 9.x.

Environment
Flutter: [flutter version]
Dart: [dart version]
flutter_downloader: [version]
Android Gradle Plugin: 9.1.0
Gradle: 9.1.0
Java: 17+
Android SDK: [version]
Additional information

Flutter's newer project templates now use AGP 9.x, and AGP 9 introduces changes such as Built-in Kotlin and the new Android Gradle DSL. Flutter has also documented that plugins need to migrate their Android build configuration for AGP 9 compatibility.

Please consider updating flutter_downloader's Android Gradle configuration accordingly.

Thank you.

No specific file or test is named. Start by inspecting flutter_downloader's Android Gradle configuration and compare it with Flutter's documented AGP 9 migration requirements; verify the plugin builds in a current Flutter project using AGP 9.x, Gradle 9.x, and Java 17.

Written by the indexing model from the issue text.