feat: add service monitoring alerts for Gitea, Postfix, Dovecot, OpenLDAP, and WireGuard, and consolidate alerting rules in Grafana

hosts/web-arm/modules/grafana/alerting/service/default.nix

@@ -0,0 +1,16 @@
+{ lib, pkgs, config, ... }:
+let
+  serviceDownAlertRules = (import ./service_down.nix { inherit lib pkgs config; }).grafanaAlertRuleDefinitions;
+
+  allServiceRules = serviceDownAlertRules;
+in
+{
+  services.grafana.provision.alerting.rules.settings.groups = [
+    {
+      name = "Service Alerts";
+      folder = "Service Monitoring";
+      interval = "1m";
+      rules = allServiceRules;
+    }
+  ];
+}