gitea: add actions runner and CI/CD deploy workflow

This will avoid me having to run "deploy" myself on my laptop.
All I will need to do is push a commit and it will self-deploy.

configuration.nix

@@ -26,6 +26,7 @@
     ./services/caddy.nix
     ./services/immich.nix
     ./services/gitea.nix
+    ./services/gitea-actions-runner.nix
     ./services/minecraft.nix
 
     ./services/wg.nix
@@ -73,6 +74,10 @@
     ./services/mollysocket.nix
   ];
 
+  # Hosts entries for CI/CD deploy targets
+  networking.hosts."192.168.1.50" = [ "server-public" ];
+  networking.hosts."192.168.1.223" = [ "desktop" ];
+
   services.kmscon.enable = true;
 
   systemd.targets = {
@@ -249,6 +254,14 @@
 
   users.groups.${service_configs.media_group} = { };
 
+  users.users.gitea-runner = {
+    isSystemUser = true;
+    group = "gitea-runner";
+    home = "/var/lib/gitea-runner";
+    description = "Gitea Actions CI runner";
+  };
+  users.groups.gitea-runner = { };
+
   users.users.${username} = {
     isNormalUser = true;
     extraGroups = [