feat: update example for android platform

[ivtimur]

This PR updates the example/android project to the modern Flutter/Android Gradle setup so the example app runs again.

What changed

• Migrated Android build configuration to the plugin-based Gradle format (plugins { ... }) instead of legacy apply plugin/apply from.
• Updated Gradle Wrapper from 7.5 to 8.11.1.
• Updated Android DSL to current syntax:
  • compileSdkVersion -> compileSdk
  • minSdkVersion/targetSdkVersion -> minSdk/targetSdk
• Upgraded Java/Kotlin targets from 1.8 to 17.
• Reworked settings.gradle to use Flutter plugin management (pluginManagement, includeBuild(...), plugin declarations).
• Removed deprecated buildscript configuration from example/android/build.gradle.

Why

The previous Android configuration in example was outdated and incompatible with the current Flutter/Gradle/AGP toolchain, causing the app to fail at launch/build time.
This update aligns the project with the current Android build requirements and restores normal startup.