📝 Simplify error message for non-existent user in password recovery

[Musbi8788]

This PR improve the error message on the login.py for better UX

Updated the response message from:

• "The user with this username does not exist in the system."
  to:
• "User does not exist"

This makes the reponse shoter and remove unnessary message like ".... username don't exit in the system" for better security with telling fake users that the name don't exist in the system instead we can just tell them the user does not exist.

Checklist

• This PR is an obvious typo fix, or it links to a GitHub Discussion for the proposed code change.
• I added tests for the change.
• The new or updated tests fail on the main branch and pass on this PR.
• Coverage stays at 100%.
• The documentation explains the change if needed.

[github-actions]

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[Musbi8788]

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Thank you for this update am updating the PR