fix(tests): update tests for lazy app loading and 302 redirect

- test_gui_scaffold.py: use standalone router instead of importing app
  to avoid triggering settings load during test collection
- test_setup_gate.py: expect 302 (not 307) for setup gate redirect

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/test_setup_gate.py

@@ -83,7 +83,7 @@ class TestSetupGateMiddleware:
             client = TestClient(app, follow_redirects=False)
 
             response = client.get("/")
-            assert response.status_code == 307
+            assert response.status_code == 302
             assert response.headers["location"] == "/setup"
 
     @pytest.mark.asyncio