hotfix: Email addresses should be case insensitive

[Soxasora]

Description

Emails are stored in lower-case and the verification is case-sensitive.
This PR converts the email address saved in session storage to lower case at the time of callbackUrl building, preventing unexpected login errors.

Screenshots

Additional Context

Code-entering page displays the email inserted by the user as-is to maintain the email as expected by the user, this fix operates behind the scenes

Checklist

Are your changes backwards compatible? Please answer below:
Yes

On a scale of 1-10 how well and how have you QA'd this change and any features it might affect? Please answer below:
7, inserted all types of emails, as long as the email is correct whether UPPERCASE or lowercase it can't give an error.

For frontend changes: Tested on mobile, light and dark mode? Please answer below:
n/a

Did you introduce any new environment variables? If so, call them out explicitly here:
No