fix: read gateway token from secret file via bash

modules/nixos/services/openclaw_node.nix

@@ -50,18 +50,13 @@ in {
         Group = cfg.user;
         WorkingDirectory = "/home/${cfg.user}";
         ExecStart = ''
-          ${openclawPkg}/bin/openclaw \
-            node run \
-            --host ${cfg.gatewayHost} \
-            --port ${toString cfg.gatewayPort} \
-            --display-name "${cfg.displayName}"
+          ${pkgs.bash}/bin/bash -c 'export OPENCLAW_GATEWAY_TOKEN=$(cat ${cfg.gatewayTokenFile}) && exec ${openclawPkg}/bin/openclaw node run --host ${cfg.gatewayHost} --port ${toString cfg.gatewayPort} --display-name "${cfg.displayName}"'
         '';
         Restart = "always";
         RestartSec = 5;
       };
 
       environment = {
-        OPENCLAW_GATEWAY_TOKEN_FILE = cfg.gatewayTokenFile;
         NODE_ENV = "production";
       };
     };