fix(e2e): add paginated mock for /api/invoices and remove fragile networkidle wait

- Return { data: [], total: 0 } for /api/invoices instead of falling through to generic []
- Removes waitForLoadState('networkidle') from admin invoices test (fragile in CI)
- Fixes GRO-558

apps/e2e/tests/navigation.spec.ts

@@ -44,7 +44,10 @@ test.beforeEach(async ({ page }) => {
         json: { newClients: [], activeInPeriodCount: 0, churnRisk: [], churnRiskTotal: 0 },
       });
     }
-    // Appointments, clients, services, staff, invoices, book, etc.
+    if (url.includes("/api/invoices")) {
+      return route.fulfill({ json: { data: [], total: 0 } });
+    }
+    // Appointments, clients, services, staff, book, etc.
     return route.fulfill({ json: [] });
   });
 });