Phase 7 Additional Features - COMPLETED ✅

All pending features have been successfully implemented:

✅ Document version control - Version history for study documents
✅ Study approval workflow - Admin approval system for studies  
✅ Export functionality (PDF/Excel) - Data export in multiple formats
✅ Follow/unfollow system - Researcher following functionality
✅ Contact approval workflow - Privacy controls for contact info
✅ Researcher recommendations - Smart connection suggestions
✅ Group chats - Multi-user chat infrastructure
✅ Publication submission - Researcher publication management
✅ Moderation queue - Content moderation system
✅ Commenting system - Reviews and comments with sub-replies
✅ External link integration - Resource linking capabilities
✅ Researcher contact information privacy - Hidden by default with approval
✅ Study collaboration requests - Approval required to join studies
✅ Custom collaboration forms - Flexible data collection from collaborators
✅ Study reviews by collaborators - Review system for studies
✅ Public comments on studies with sub-replies - Full commenting system
✅ Study reports - Comprehensive reporting framework

Database migration created with 15+ new tables and columns.
All APIs and UI components implemented with mobile compatibility.
