Add runner for Forgejo actions

system/services/forgejo.nix

@@ -1,4 +1,8 @@
-{...}: {
+{
+  config,
+  pkgs,
+  ...
+}: {
   imports = [./caddy.nix];
   services = {
     forgejo = {
@@ -16,6 +20,16 @@
         service = {DISABLE_REGISTRATION = true;};
       };
     };
+    gitea-actions-runner = {
+      package = pkgs.forgejo-runner;
+      instances.default = {
+        enable = true;
+        name = "monolith";
+        url = config.services.forgejo.settings.server.ROOT_URL;
+        tokenFile = /var/lib/forgejo/runner_registration_token;
+        labels = ["native:host"];
+      };
+    };
     caddy.virtualHosts."git.xenia.me.uk".extraConfig = "reverse_proxy http://localhost:3100";
   };
 }