Less false positive alerts on monthly backup checks after reboot

nixos/modules/monitoring/server/grafana-dashboards/backups.json

@@ -545,14 +545,31 @@
             },
             "query": {
               "params": [
-                "A",
-                "5m",
-                "now"
+                "A"
+              ]
+            },
+            "reducer": {
+              "type": "last"
+            }
+          },
+          {
+            "evaluator": {
+              "params": [
+                -30758400
+              ],
+              "type": "gt"
+            },
+            "operator": {
+              "type": "and"
+            },
+            "query": {
+              "params": [
+                "A"
               ]
             },
             "reducer": {
               "params": [],
-              "type": "avg"
+              "type": "last"
             },
             "type": "query"
           }