Built signature page and updated profile to show signature status

[sheggen]

Issue Description

Fixes issue #1739

Changes

Signatures:

• Adds a signature field to each user's profile. The signature field is only accessible to:
  • the user whose profile you are viewing (i.e., no one can sign on someone else's behalf).
  • the user if they are attending or have attended All volunteers training (for non-labor students)
  • the user if they are attending or have attended All CELTS training (for labor students)
  • the CELTS staff have uploaded the appropriate handbook for each case above
• Only one signature is needed for an academic year
• Program Managers can view signature statuses in Rosters (see below)

Rosters

• Program Managers and admins can view rosters for participants in their program:
  • All interested volunteers (checked the box in their profile or in the extravaganza page)
  • All active volunteers (have earned service hours in their program)
  • All previous year's volunteers (earned service hours last AY)
• Rosters can be exported to Excel

Volunteer Extravaganza

• Added a page for the volunteer Extravaganza (/extravaganza).
• TODO: Add a QR code somewhere in the admin interface for them to download and use on flyers at the extravaganza

Term Management

• CELTS admins can now upload:
  • All Volunteers Handbook (for all volunteers)
  • All CELTS Handbook (for labor)
  • The Background check form (which students will need to submit to Sheila in paper format, due to SSN and other private info we do not want to store)
• All three files above are stored for an AY, depending on the selected term (i.e., If the form is uploaded in Summer 2026, it applies to Fall 25, Spring 26, and Summer 26)

Event Templates

• Added two new event templates: All CELTS training and Weekly Labor Meeting

Testing

Signature Workflow

• Reset your database (test) and run the app.
• Set the user to an admin or Program Manager
• View your profile. You should not be able to sign anything yet.
• Set the current term, then upload a handbook (all volunteer or celts labor).
• Create a new All Volunteers/All CELTS labor event in the future. RSVP a user. Check that the user cannot sign the handbook yet (as the event hasn't happened yet)
• Move the event into the present or past. Mark the user as "attended". Try signing again (they should be able to sign now).
• After the handbook is signed, test that it persists for the current academic year, and then resets during the following AY.

Rosters

• Pick a program to test against. Mark a user as "interested" in the program. Check the roster as a PM and as an admin.
• Add an event to the program. Add the user to the event. Check the roster (specifically, the "Engaged Volunteers" section).
• Add an event to the program in the previous academic year, and add a user to that event. Check the roster (specifically, the "Last Year's Volunteers" section).
• Export the rosters and confirm the data matches on the spreadsheet.

Event Templates

• Create events using each template. In particular, test recurring events for labor meetings.

Remaining Tasks

• Prevent a user from participating in an event that earns service hours if they have not completed the four requirements (signed the handbook, attended AVT, attended PST, and have submitted their background check form).
• How do we handle RSVPs vs. attended in the rosters?
• QR code for the extravaganza plus links to that page somewhere in the admin interface
• New functions need tests written
• How does /extravaganza look on a mobile, since that is how most will use it on that day?