Add instasync cronjob and plumbing for nodejs on nomad clients.

hosts/common/global/packages.nix

@@ -1,6 +1,7 @@
 { pkgs, ... }:
 {
   environment.systemPackages = with pkgs; [
+    nodejs_20
     vim
   ];
 }

hosts/common/nomad.nix

@@ -22,9 +22,15 @@ in
           interface = "tailscale0";
           cidr = "100.64.0.0/10";
         };
-        host_volume.code = {
-          path = "/data/compute/code";
-          read_only = true;
+        host_volume = {
+          code = {
+            path = "/data/compute/code";
+            read_only = true;
+          };
+          nix-store = {
+            path = "/nix/store";
+            read_only = true;
+          };
         };
       };