Migrate from Imperative to Declarative Gradle Plugin Application

[BrutalCoding]

Description

• The project currently uses the deprecated apply method for configuring the app_plugin_loader Gradle plugin.
• This method will be removed in future Flutter releases.

Tasks

• Migrate to using the declarative plugins block for configuring Gradle plugins.
• Reference the official Flutter migration guide: https://flutter.dev/go/flutter-gradle-plugin-apply