US08 - Implement User Login Backend Service API

[RamirezJM]

As a Registered User
I need to log in using my credentials (email and password)
So that I can obtain a secure authentication token to access protected API endpoints.

Details and Assumptions

• Authentication will likely issue a JSON Web Token (JWT) upon successful login.
• The system must handle failed login attempts securely without leaking account information.

Acceptance Criteria

Given a user provides correct login credentials
When a POST request is sent to the login endpoint
Then the system should return a 200 OK status along with a valid authentication token