feat: Auth final

[ap0nia]

Summary

• Frontend implementation of auth.
• Uses current DynamoDB without migrating to RDS yet.

Refinements

• If user is not logged in, they should not be able to change visibility.
• If user is not logged in, they're allowed to pick any user ID to save.
• If user is is logged in, the user ids to save the schedule under is readonly.
• Toggle visibility settings in account dialog.

Test Plan

Future Follow-Up

• Migrate system to RDS.