First Dockerfile version for frontend

[pjuaristi-ikerlan]

Description

Closes issue #111

This PR introduces the first version of the Dockerfile to build the React app with Node.js and serve it via Nginx with dynamic environment variable injection.

The environment variable injection has been done following the approach of the portal frontend with some modifications.

Acceptance Criteria

• A functional Dockerfile exists in the repository.
• The frontend builds and runs successfully in a containerized environment.
• Dynamic ENV are injected successfully

Pre-review checks

Please ensure to do as many of the following checks as possible, before asking for committer review:

• DEPENDENCIES are up-to-date. Dash license tool. Committers can open IP issues for restricted libs.
• Copyright and license header are present on all affected files

[sonarqubecloud]

Quality Gate failed

Failed conditions
2 Security Hotspots

See analysis details on SonarQube Cloud