Include Sonar Cloud into project

[EnricoBausenhart]

We want to integrate SonarCloud into the project to enable static code analysis and improve code quality over time. This will help us catch bugs, security vulnerabilities, and code smells early in the pipeline.

The integration should support automatic analysis on every push and pull request, within the Github Actions pipeline.

DOD:

• Set up SonarCloud project (if not already created)
• Generate and configure project token securely (use repository secrets)
• Add sonar-project.properties or equivalent config file to the repo
• Integrate SonarCloud into CI pipeline
• Ensure analysis runs on PRs and shows up in the SonarCloud dashboard