feat(hosts,lib): use kube-vip for k3s's HA

hosts/k8s/k3s-prod-1-master-2/default.nix

@@ -6,7 +6,6 @@
   ...
 }: let
   hostName = "k3s-prod-1-master-2"; # define your hostname.
-  k3sServerName = "k3s-prod-1-master-1";
 
   coreModule = mylib.genKubeVirtCoreModule {
     inherit pkgs hostName;
@@ -16,7 +15,9 @@
     inherit pkgs;
     kubeconfigFile = "/home/${myvars.username}/.kube/config";
     tokenFile = config.age.secrets."k3s-prod-1-token".path;
-    serverIp = myvars.networking.hostsAddr.${k3sServerName}.ipv4;
+    # use my own domain & kube-vip's virtual IP for the API server
+    # so that the API server can always be accessed even if some nodes are down
+    masterHost = "prod-cluster-1.writefor.fun";
   };
 in {
   imports =