Manual Admin Checkin

[joshuasilva414]

Admins must be able to add checkins manually for users who's QR codes cannot be scanned

Requirements

• "Add Checkin" button under the ellipses (triple dots) on the user table
• "Add Checkin" button at the top of the /admin/users page
• Shows modal when add checkin button is pressed
• Modal must take in hackertag
• Show toasts on success, warning, or error
• Must pre-fill hackertag field

[linear]

HK-214