Feat/auth updates

[khanhdo05]

Changes made

• Resolved Bug: Registered display name not saved and rendered upon sign-up.
• Added Email verification feature upon sign up: The flow is now: Go to Sign Up form -> fill out info -> click Sign Up -> Email sent -> User verified their account -> Go back to StressLess webstie -> get authorized and authenticated -> redirect to /preference
• Added Forget password feature to the Sign In form.
• Made all error messages from Firebase more user-friendly.
• Added Preview password feature
• WIP: Debug fetching and rendering old events

Some screenshots