feat(ci): add CI/CD pipeline configuration
- Added .gitlab-ci.yml file to define CI/CD pipeline stages: build, test, and deploy
- Configured build job to clean and package the project using Maven
- Configured test jobs to run Maven tests
- Configured deploy job to build, push, and run Docker image for production environment
- Set up environment variables and conditions for deployment to production
This commit sets up a comprehensive CI/CD pipeline to automate the build, test, and deployment processes for the project.