feat: [245] Update user signup success and error messages

[mmnoo]

after a suer signs up successfully, they will see a toast and message on the login page they are navigated to saying to check their email.

to test:

• go to the sign up page
• sign up
• see the toast and message on the login page when redirected

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[julia-rom]

This works, something else that could improve the user flow is disabling the sign up button after it is clicked and adding some sort of indictor (ex: submitting, verifying, signing up, etc)

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