VxDesign: proofing status to confirm export readiness

[mattroe]

After configuring all ballots and reviewing the ballot renders, customers should have the ability to confirm that ballots have been proofed and are ready for VotingWorks to export/convert packages and PDFs. VotingWorks also needs to be notified that ballots are ready for export, but that can be tackled separately as part of #5813

An election official will want to review ballots on a per ballot style basis. For initial use in NH spring elections, an election official will only need to proof two styles (town/school) so support for proofing state by style is not strictly necessary. Proofing status does not need to be tracked for official vs. test vs. sample nor precinct vs. absentee.

[jonahkagan]

Implemented a basic button to finalize all ballots. I think we should add a follow up that locks all editing of the election after finalizing. And also a way to undo using internal tools.