Create new Playwright tests to validate sign in and registration

[evadecker]

Create a new test within tests/e2e to test the end-to-end flow for signup, registration, and password reset.

Test cases

Registration

• Displays an error message displays when fields are invalid; form does not submit
• Displays a success message when submitting a valid registration
• Alerts the user if the email address for registration already exists (requires Write unit test for StatusSelect #294)

Password reset

• Displays an error message if the account is not found
• Displays the code entry success message and input if the code was sent
• Allows entering the emailed code and resetting the password (will require mocking)

Sign in

• Displays an error message if email does not belong to a registered user (requires Display an error message on registration if the email is already registered #295)
• Displays error message if the email or password fields are invalid (malformatted email or empty)
• Logs the user in and redirects after successful submission

Because we haven't written many Playwright tests for Namesake yet, when tackling this ticket it may be necessary to create additional test helpers or configuration in order to simplify the test writing process. If it seems likely that other Playwright tests will require similar mocks or helpers, consider abstracting them somewhere reusable.