feat: Multi-user review + third-party uploads to a project (team/hosted)

[markkerzner]

Why

David Berenthal noted his online platform allows third parties to upload documents to a project and supports multiple reviewers — currently beyond FreeEed's single-machine desktop workflow.

Scope

• Multiple reviewers on one project.
• Third-party document upload into an existing project.
• Team/hosted direction (vs single-machine).

Asked by

David Berenthal.