fix(nixos): disable Gitea registration

configs/nixos/modules/services/gitea.nix

@@ -57,7 +57,7 @@ in
             SSH_LISTEN_PORT = 2222;
             REVERSE_PROXY_TRUSTED_PROXIES = "${cfg.reverseProxyAddress}/32";
           };
-          service.DISABLE_REGISTRATION = false;
+          service.DISABLE_REGISTRATION = true;
           # Direct bootstrap access uses HTTP until the public HTTPS route moves.
           session.COOKIE_SECURE = false;
         };