fix(alerts): evaluate fresh reports and order notification delivery (#1242)

* fix(alerts): evaluate fresh reports and make notification transitions reliable

* fix(alerts): identify equal-timestamp reports by sequence

* fix(alerts): preserve notification transition semantics

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Co-authored-by: naiba <hi@nai.ba>

service/singleton/server.go

@@ -117,6 +117,7 @@ func (c *ServerClass) Update(s *model.Server, uuid string) {
 func (c *ServerClass) Delete(idList []uint64) {
 	c.lockLifecycleWrite()
 	defer c.unlockLifecycleWrite()
+	cancelAlertDeliveriesForServers(idList)
 
 	c.listMu.Lock()