[DRAFT] Built signature page and updated profile to show signature status

[sheggen]

Issue Description

Fixes issue #1739

Changes

• Adds a signature page to CELTS-Link (/handbookSignature). The page is only accessible by CELTS staff and Program Managers.
• Stores the date of the signature of the volunteer. The page must be accessed by a staff/PM, where they can then sign it.
• User profile now shows that status of your signature. It goes red when there is a) no signature on file or b) the signature is more than a year old.

Testing

• Reset your database and run the app.
• Set the user to an admin or Program Manager
• Navigate to /handbookSignature
• Fill out the form.
• Check the profile of the student who signed.

Remaining Tasks

• Prevent a user from participating in an event that earns service hours.
• Generate reports for CELTS staff about who has/has not signed.