Sign-up with existing email loops; should prompt for login instead

[arishta]

Steps to Reproduce:

1. Select the login method: New user, sign up.
2. Enter the email and password of an existing user.
3. The CLI throws an error: Account already exists and loops back to the sign-up screen instead of guiding the user to log in with the existing credentials.

Observed Behavior:

As shown in the screenshot, attempting to sign up with an email already associated with an existing account results in the error: Account already exists. The CLI then repeatedly takes the user back to the sign-up process. This forces the user to terminate the process manually and start a new login attempt.

Expected Behavior:

Instead of reloading the sign-up flow, the system should recognize the account already exists and prompt the user to log in with their existing credentials.

Suggested Improvement:

To enhance the user experience:

If the email provided during sign-up matches an existing account, the CLI should display a message like:
This email is already associated with an account. Please log in instead.

Automatically redirect the user to the login flow, allowing a seamless transition without requiring the user to restart the process manually.