- Add GET /api/admin/activity with pagination and filters
- Add GET /api/admin/users/:id/activity for user-specific history
- Add GET /api/admin/activity/export for CSV export
- Implement $lookup aggregation for user info (name, email)
- Add date range filtering with validation
- Export limited to 10,000 records with truncation headers
- All 50 Phase 2 tests passing
- Configure Jest with mongodb-memory-server for isolated testing
- Add phase 1-4 test suites covering all admin requirements
- Add test helpers and setup/teardown utilities
- Install jest, supertest, mongodb-memory-server dependencies
