- Add GET /api/admin/settings for configuration retrieval
- Add PATCH /api/admin/settings with validation (30-365 days)
- Implement TTL index update when retention period changes
- Add last admin protection (cannot demote last active admin)
- Add audit logging for admin actions (ADMIN_UPDATE_SETTINGS, etc.)
- 45/52 Phase 4 tests passing (7 rate limiting tests not in scope)
- Add GET /api/admin/stats/overview (user counts, login stats)
- Add GET /api/admin/stats/active-users (time series with period toggle)
- Add GET /api/admin/stats/actions (action breakdown with date filter)
- Add GET /api/admin/stats/peak-times (hourly/daily averages)
- Implement 5-minute in-memory caching for expensive aggregations
- All 57 Phase 3 tests passing
- 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
- Add database indexes for admin queries (role, isActive+role, createdAt, lastLoginAt)
- Update setUserActive to track disabledAt and disabledBy fields
- Add getPaginatedUsers function with search, filter, sort support
- Add updateUserRole function for promoting/demoting users
- Create admin routes with full user management API:
- GET /api/admin/users - paginated list with search/filter/sort
- GET /api/admin/users/:id - user details with recent activity
- PATCH /api/admin/users/:id - enable/disable users
- PATCH /api/admin/users/:id/role - promote/demote users
- Add validation for ObjectId format and self-modification prevention
- All 53 Phase 1 backend tests passing
