- Create consent.js with comprehensive API endpoints:
- GET /api/social-media/platforms - list active platforms
- POST /api/groups/:groupId/consents - save/update group consents
- GET /api/groups/:groupId/consents - retrieve group consent data
- GET /api/admin/groups/by-consent - filter groups by consent status
- GET /api/admin/consents/export - export consent data (JSON/CSV formats)
- Register consent router in routes/index.js
- Full validation and error handling
- CSV export with dynamic platform columns
- Ready for frontend integration
