Correctness fix for multi-instance: 6 hooks gain optional serviceId in queryKey;
7 API fns append ?service_id; 4 backup endpoints gain service_id filter
(Alertmanager/Prometheus status already take it — zero backend change there);
3 tabs pass instance.id; dashboard widgets unaffected; all params optional
(backward-compat). usePrometheusTargets + useMonitoringMachines stay global.
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