fix: Address second code review findings (test isolation, frontend type safety)

backend/tests/api/test_api_auth_cookie.py

@@ -5,7 +5,9 @@ from ea_chatbot.api.main import app
 from ea_chatbot.history.models import User
 from ea_chatbot.api.utils import create_access_token
 
-client = TestClient(app)
+@pytest.fixture
+def client():
+    return TestClient(app)
 
 @pytest.fixture
 def mock_user():
@@ -17,7 +19,7 @@ def mock_user():
         theme_preference="light"
     )
 
-def test_v1_prefix():
+def test_v1_prefix(client):
     """Test that routes are prefixed with /api/v1."""
     # This should now be 404
     response = client.get("/auth/me")
@@ -27,7 +29,7 @@ def test_v1_prefix():
     response = client.get("/api/v1/auth/me")
     assert response.status_code == 401
 
-def test_login_sets_cookie():
+def test_login_sets_cookie(client):
     """Test that login sets the access_token cookie."""
     with patch("ea_chatbot.api.routers.auth.history_manager") as mock_hm:
         mock_hm.authenticate_user.return_value = User(id="1", username="test@example.com")
@@ -45,7 +47,7 @@ def test_login_sets_cookie():
         assert "access_token" in set_cookie
         assert "HttpOnly" in set_cookie
 
-def test_register_sets_cookie():
+def test_register_sets_cookie(client):
     """Test that register sets the access_token cookie."""
     with patch("ea_chatbot.api.routers.auth.history_manager") as mock_hm:
         mock_hm.get_user.return_value = None
@@ -59,7 +61,7 @@ def test_register_sets_cookie():
         assert response.status_code == 201
         assert "access_token" in response.cookies
 
-def test_auth_via_cookie():
+def test_auth_via_cookie(client):
     """Test that protected routes work with the access_token cookie."""
     token = create_access_token(data={"sub": "123"})
     
@@ -73,7 +75,7 @@ def test_auth_via_cookie():
         assert response.status_code == 200
         assert response.json()["email"] == "test@example.com"
 
-def test_logout_clears_cookie():
+def test_logout_clears_cookie(client):
     """Test that logout endpoint clears the cookie."""
     response = client.post("/api/v1/auth/logout")
     assert response.status_code == 200
@@ -81,7 +83,7 @@ def test_logout_clears_cookie():
     cookie = response.cookies.get("access_token")
     assert not cookie or cookie == ""
 
-def test_oidc_callback_redirects_with_cookie():
+def test_oidc_callback_redirects_with_cookie(client):
     """Test that OIDC callback sets cookie and redirects."""
     with patch("ea_chatbot.api.routers.auth.oidc_client") as mock_oidc, \
          patch("ea_chatbot.api.routers.auth.OIDCSession.decrypt") as mock_decrypt, \