Merge Integration to Main

This merge introduces CI/CD build stages for the following components in .gitlab-ci.yml:

• build-frontend: Installs dependencies and builds the frontend assets using the image: node:16-alpine.
• build-backend: Pulls custom image that configures the Keycloak server, installs backend dependencies, and runs the Flask application.

Upon approval, this merge adds .gitlab-ci.yml file to the main branch.