[Admin] Implement badge tracking system

[taesungh]

Logistics is looking to host a general participant raffle where attendance to workshops and social events will count as raffle entries. We'll be tracking barcodes on participant badges during check-in, and we'll also need a page for organizers to scan these barcodes at each event. These barcodes can also be used to check in participants on Saturday and Sunday.

• [PMS] Incorporate barcode input with check-in system #360
• [Admin] Create new page for tracking attendance at subevents #359
• Add endpoint to store subevent check-ins