Feature: Integrate Spotless for Code Formatting

[menny]

This PR introduces Spotless to the project to enforce consistent code formatting across Kotlin,
Gradle Kotlin DSL, and Markdown files.

Key changes include:

• Added Spotless plugin to settings.gradle.kts.
• Configured Kotlin, Kotlin Gradle, and Markdown formatting rules in build.gradle.kts, including ktfmt, trimTrailingWhitespace, and endWithNewline.
• Applied formatting changes using spotlessApply.
• Integrated spotlessCheck into the GitHub CI workflow to ensure future code adheres to the defined formatting standards.

This will help maintain code quality and readability, and reduce merge conflicts related to
formatting.