feat: platform admin backend — controllers, services, routes, tests
Add cross-organisation admin API endpoints behind role:super_admin middleware:
- AdminOrganisationController: CRUD with search, filter, billing_status management
- AdminUserController: user management with role assignment across orgs
- AdminStatsController: platform-wide aggregate statistics
- AdminActivityLogController: filterable activity log viewer
- AdminImpersonationController + ImpersonationService: user impersonation with
token-based session management and activity logging
- BillingStatus enum, form requests, API resources, 23 feature tests
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
bert.hausmans
ddf26dad33