Added simple login endpoint with tests for happy and non-happy paths

[azunaVT]

Add Login Endpoint (Authenticate User & Create Session)

This PR implements the login endpoint under the Auth namespace, allowing existing users to authenticate with their email and password. Upon successful login, a new session is created and a token is returned.

---

What’s Included

Login action in Api::V1::AuthController

• Accepts a nested user object:

  {
    "user": {
      "email": "user@example.com",
      "password": "password123"
    }
  }