feat: restructure Grafana configuration, migrate alert rules to new format and add VictoriaMetrics datasource

hosts/web-arm/modules/grafana/datasources/victoriametrics.nix

@@ -0,0 +1,18 @@
+{ lib, pkgs, config, ... }:
+{
+  services.grafana.provision.datasources.settings.datasources = [
+    {
+      name = "VictoriaMetrics";
+      uid = "vm-datasource-uid"; # Stable UID for referencing in alerts
+      type = "prometheus";
+      url = "http://localhost:8428"; # URL of VictoriaMetrics
+      access = "proxy"; # Grafana proxies requests
+      isDefault = true; # Optional: make this the default datasource
+      jsonData = {
+        # timeInterval = "30s"; # Optional: Scrape interval if different from Grafana's default
+        # httpMethod = "POST"; # Optional: if VictoriaMetrics prefers POST for queries
+      };
+      editable = false; # Recommended for provisioned datasources
+    }
+  ];
+}