forgejo-actions-runner(host): enable IPv6 support in Docker

Enable the relevant config option and move to new network with an
explicit IPv6, because otherwise there's no default v6 route and v6 in
the Docker containers doesn't work.

config/hosts/forgejo-actions-runner/configuration.nix

@@ -1,7 +1,10 @@
 { config, pkgs, ... }:
 
 {
-  networking.hostName = "forgejo-actions-runner";
+  networking = {
+    hostName = "forgejo-actions-runner";
+    domain = "hosts.hamburg.ccc.de";
+  };
 
   system.stateVersion = "23.11";
 }

config/hosts/forgejo-actions-runner/docker.nix

@@ -9,5 +9,8 @@
       enable = true;
       dates = "weekly";
     };
+    daemon.settings = {
+      ipv6 = true;
+    };
   };
 }

config/hosts/forgejo-actions-runner/networking.nix

@@ -5,14 +5,14 @@ let
 in {
   networking = {
     interfaces.net0 = {
-      ipv4.addresses = [
+      ipv6.addresses = [
         {
-          address = "172.31.17.155";
+          address = "2a00:14b0:42:102::18";
-          prefixLength = 25;
+          prefixLength = 64;
         }
       ];
     };
-    defaultGateway = "172.31.17.129";
+    defaultGateway6 = "2a00:14b0:42:102::1";
     nameservers = [ "212.12.50.158" "192.76.134.90" ];
     search = [ "hamburg.ccc.de" ];
   };

deployment_configuration.json

@@ -9,9 +9,6 @@
     "git": {
       "targetHostname": "git.hamburg.ccc.de"
     },
-    "forgejo-actions-runner": {
-      "targetHostname": "forgejo-actions-runner-intern.hamburg.ccc.de"
-    },
     "woodpecker": {
       "targetHostname": "woodpecker-intern.hamburg.ccc.de"
     },