Introduce Spotless and apply formatting to entire project

[BartoszLitwiniuk]

Description

This PR introduces Spotless to the project and applies formatting to all source files based on the configured rules.

Purpose

• To establish a consistent and automated code formatting standard across the project.
• To ensure future commits remain clean and free from unnecessary formatting diffs.

Details

• Added Spotless configuration to the Gradle build setup.
• Defined formatting rules for Java, JSON, gradle and markdown files.
• Applied formatting to all project files using ./gradlew spotlessApply.
• The configuration and reformat were previously reviewed separately to allow a clear review process.

Verification

• Run ./gradlew spotlessCheck — all files should pass.
• Project builds and runs successfully after applying the formatting.

Next steps

• Going forward, Spotless will automatically enforce formatting during builds or CI checks.

[BartoszLitwiniuk]

This PR can be changed to 'Ready for review' when #191 will be merged to this branch.