Implemented Box Management API

[anthonyzhao27]

Summary

Added Box API support (list/detail), Box description field + migration, and item box assignment via authenticated PATCH; included tests and lint config to keep flake8 clean.

Enables “add to boxes” by letting the system track which items are inside each box and reliably update an item’s box_id, which was a core requirement in the issue.

Related Issues

• Closes Box Management API #32

Changes

• Create Box entity in the database (ID, Label/Number, Description).
• Update CollectionItem table to add a nullable box_id foreign key.
• Implement GET /api/boxes to list all boxes.
• Implement GET /api/boxes/:id to return box details AND the list of items currently inside.

How to Test

1. cd backend/inventory && pytest

Checklist

• Tests added or updated
• CI passes (lint, tests, build)
• Documentation updated (if behavior changed)
• No secrets or credentials committed

[vivjd]

LGTM! Just as a side note, if you notice issues with the any configs (e.g. lint) in the future, please make a separate PR for it so we can keep our work flow clean!