feat(circuit): add numUsager to list API and deactivated circuit assignments
- Expose numUsager in GET circuit driver assignment list response (count usagers in period)
- Create/update inactive CircuitDriverAssignment when trip assignments are deactivated (reassignment, amendment, planning unassign): single row per (circuitId, driverUuid), merge period, trip ids and weekly schedule; fallback on existing inactive when no overlap
- TripDriverAssignmentServiceImpl: call createDeactivatedCircuitAssignmentsForDeactivatedTrips from deactivateAssignment, deactivateAssignments, performSplittingForAssignmentWithObservation, and deactivateAssignmentsByAmendment .