R1: exclude status=demo entities from alert traversal (alert_generator / deviation_engine / kpi_bep_deriver / alert_rules / cash engine)
R2: only generate alerts within the last 6 calendar months (incl. current)
R3: only regular month periods (YYYY-MM) participate
R4: decouple generation from push - empty notification_channels never blocks
Single source of truth: app/utils/alert_entity_scope.py