fix: update Blackbox Exporter scrape config and Grafana alert expressions for improved monitoring accuracy

hosts/web-arm/modules/blackbox-exporter.nix

@@ -33,23 +33,30 @@ in {
     # Add scrape config for VictoriaMetrics agent
     services.victoriametrics.extraScrapeConfigs = [
       ''
-      - job_name: "blackbox_http_all_domains"
-        metrics_path: "/probe"
-        params:
-          module: ["http_2xx"]
+        - job_name: "blackbox_http_all_domains"
+          metrics_path: "/probe"
+          params:
+            module: ["http_2xx"]
 
-        static_configs:
-          - targets:
-              [
-                ${domainsString}
-              ]
+          static_configs:
+            - targets:
+                [
+                  ${domainsString}
+                ]
 
-        relabel_configs:
-          - source_labels: ["__address__"]
-            target_label: "__param_target"
-            replacement: "$$1"
-          - source_labels: ["__param_target"]
-            target_label: "instance"
+          relabel_configs:
+            - source_labels: ["__address__"]
+              target_label: "__param_target"
+              regex: '(.*)'
+              replacement: "$1"
+            - source_labels: ["__param_target"]
+              target_label: "instance"
+            - target_label: "__address__"
+              replacement: "127.0.0.1:9115"
+            - source_labels: ["__address__"]
+              regex: "127\\.0\\.0\\.1:9115"
+              target_label: "__scheme__"
+              replacement: "http"
       ''
     ];
   };