Fix adminResolveReport in Admin UI

[Mephistic]

Describe the bug
The adminResolveReport is currently broken - it looks like the firebase function encounters a type error due to the Firestore Timestamp issue on the nextDigestAt field on profile documents, so admins cannot resolve reports through the Admin UI.

To Reproduce
Steps to reproduce the behavior:

1. Report a testimony (by navigating to a bill with testimony and filling out a Report)
2. As an admin user, navigate to the Admin page (at /admin)
3. Attempt to resolve the reported testimony from step 1
4. See error

Expected behavior
The Admin resolve report flow should work correctly - so completing the form on the Admin page should either reject the report (and leave the testimony in place) or accept the report (and delete the reported testimony).