Restore gateway smoke helpers after route spec cleanup

Keep the gateway health-card smoke test runnable after removing the stale replication-management helper block.

tests/e2e/superuser-system-status.smoke.spec.js

@@ -38,6 +38,59 @@ async function installSystemStatusMock(page, snapshot) {
   });
 }
 
+function createGateway(id, overrides = {}) {
+  return {
+    id,
+    label: `Gateway ${id}`,
+    hostname: `gateway-${id}.truckwash.test`,
+    department_id: 11,
+    status: "ONLINE",
+    discovery_status: "READY",
+    last_heartbeat_at: "2026-04-08T09:00:00.000Z",
+    active_operation: null,
+    diagnostics: [],
+    error_state: null,
+    ...overrides,
+  };
+}
+
+function createGatewayFleetUsage(rows) {
+  return {
+    gateways: {
+      total: rows.length,
+      online: rows.filter((gateway) => gateway.status === "ONLINE").length,
+      degraded: rows.filter((gateway) => gateway.status === "DEGRADED").length,
+      offline: rows.filter((gateway) => gateway.status === "OFFLINE").length,
+    },
+  };
+}
+
+async function installGatewayFleetMock(page, { rows, departments }) {
+  await page.route(/\/edge-gateways(?:\?.*)?$/, async (route) => {
+    await route.fulfill(
+      json({
+        success: true,
+        data: rows,
+        meta: {
+          fleet_usage: createGatewayFleetUsage(rows),
+        },
+        includes: {},
+      })
+    );
+  });
+
+  await page.route(/\/departments(?:\?.*)?$/, async (route) => {
+    await route.fulfill(
+      json({
+        success: true,
+        data: departments,
+        meta: {},
+        includes: {},
+      })
+    );
+  });
+}
+
 const degradedSnapshot = {
   overall_status: "degraded",
   generated_at: "2026-04-08T08:45:00.000Z",