[Enhancement proposal]: Migrate plugin to Flutter's built-in Kotlin (AGP 9.0 compatibility)

[rolinbos]

Please check the following before submitting a new issue.

• I have searched the existing issues.
• I have carefully read the documentation and verified I have added the required platform specific configuration.

Please select affected platform(s)

• Android
• iOS

Proposal

As of Android Gradle Plugin (AGP) 9.0, the Android build system handles Kotlin natively. Manually applying the Kotlin Gradle Plugin (KGP) now causes a conflict and results in build failures. Flutter 3.44 includes temporary backward compatibility, but this will be removed in a future release.
If this plugin is not migrated, apps using it with AGP 9.0 will fail to build. Since only plugin authors can fix this, it's on us to resolve.

What needs to be done:

• Remove the manual KGP application from the plugin's Gradle build files
• Update pubspec.yaml to set a minimum Flutter version constraint of 3.44
• Test the plugin against AGP 9.0 / Flutter 3.44+ to confirm the build works correctly
• Verify backward compatibility during the transition period