[Issue]: Central ASP.NET Core API with PostgreSQL connection #11

Branch Name

feature/11-api-postgres.

Task

Description
Create the base of the central API and connect it to PostgreSQL. It only needs to cover the basics for now, as the foundation for all later work.

Scope

• ASP.NET Core project structure
• Health endpoint
• PostgreSQL connection through Entity Framework Core
• Configuration through environment variables

Acceptance Criteria

• The API runs locally
• The health endpoint reports whether the database is reachable
• No credentials are committed to the repository

Checklist

• I have checked for duplicate issues.
• I have assigned the issue to the correct project board.
• I have tagged the issue properly.

Code of Conduct

• I agree to follow this project's Code of Conduct