fix(gateway): remove recursive ExecStop from systemd units, extend TimeoutStopSec to 60s

* fix(gateway): avoid recursive ExecStop in user systemd unit

* fix: extend ExecStop removal and TimeoutStopSec=60 to system unit

The cherry-picked PR #1448 fix only covered the user systemd unit.
The system unit had the same TimeoutStopSec=15 and could benefit
from the same 60s timeout for clean shutdown. Also adds a regression
test for the system unit.

---------

Co-authored-by: Ninja <ninja@local>

tests/hermes_cli/test_gateway_service.py

@@ -53,6 +53,23 @@ class TestSystemdServiceRefresh:
         ]
 
 
+class TestGeneratedSystemdUnits:
+    def test_user_unit_avoids_recursive_execstop_and_uses_extended_stop_timeout(self):
+        unit = gateway_cli.generate_systemd_unit(system=False)
+
+        assert "ExecStart=" in unit
+        assert "ExecStop=" not in unit
+        assert "TimeoutStopSec=60" in unit
+
+    def test_system_unit_avoids_recursive_execstop_and_uses_extended_stop_timeout(self):
+        unit = gateway_cli.generate_systemd_unit(system=True)
+
+        assert "ExecStart=" in unit
+        assert "ExecStop=" not in unit
+        assert "TimeoutStopSec=60" in unit
+        assert "WantedBy=multi-user.target" in unit
+
+
 class TestGatewayStopCleanup:
     def test_stop_sweeps_manual_gateway_processes_after_service_stop(self, tmp_path, monkeypatch):
         unit_path = tmp_path / "hermes-gateway.service"