Implement archive functionality and reviewer self-removal from reviews

**Type:** Feature Request

**Description:**
Two distinct features are needed:
1. **Archive functionality**: Allow fact-checks to be archived (soft-deleted) from any state in the workflow
2. **Reviewer self-removal**: Allow reviewers to remove themselves from a review and send it back to the fact-checker

**Acceptance Criteria:**

**For Archive Feature:**
- Add "Archive" action available from any workflow state
- Implement as soft-delete (data retained but hidden from active view)
- Add "Archived" filter to view archived items
- Include unarchive capability for admins

**For Reviewer Self-removal:**
- Add "Remove myself from review" option for reviewers
- Automatically reassign to fact-checker when reviewer removes themselves
- Send notification to fact-checker about the reassignment
- Log the action for audit trail