all: setup prometheus node exporter for all hosts on Chaosknoten

Do that so we can have monitoring for them via prometheus, alertmanager
and grafana.
Also add a local ip for the git host for PVE firewalling.

config/extra/prometheus-exporter.nix

@@ -0,0 +1,8 @@
+{ ... }:
+
+{
+  services.prometheus.exporters.node = {
+    enable = true;
+    openFirewall = true;
+  };
+}

config/hosts/git/networking.nix

@@ -11,6 +11,10 @@
           address = "212.12.51.136";
           prefixLength = 28;
         }
+        {
+          address = "172.31.17.154";
+          prefixLength = 25;
+        }
       ];
       ipv6.addresses = [
         {