Event Sign-In UI

[zbreit]

Create a demo UI for organizers to sign users into arbitrary events. This component will:

1. Render a selectable list of events (you can use the mock event data currently in the hacker mobile app repository). This list should only show active events or events that will start in fewer than 30 minutes or have ended in the last 30 minutes.
2. When an organizer selects an event, they can scan any number of attendee NFC wristbands
   • After scanning, it will display whether the user has signed into the event before