Make invalid search input explicit in UI and API

tests/test_api.py

@@ -196,3 +196,28 @@ def test_api_combined_filters_respect_same_player_season_context(client):
     )
     assert response.status_code == 200
     assert response.json()["count"] == 0
+
+
+@pytest.mark.django_db
+def test_players_api_returns_400_for_invalid_numeric_filter(client):
+    response = client.get(reverse("api:players"), data={"points_per_game_min": "abc"})
+    assert response.status_code == 400
+    payload = response.json()
+    assert payload["detail"] == "Invalid search parameters."
+    assert "points_per_game_min" in payload["errors"]
+
+
+@pytest.mark.django_db
+def test_players_api_returns_400_for_invalid_choice_filter(client):
+    response = client.get(reverse("api:players"), data={"sort": "not-a-sort"})
+    assert response.status_code == 400
+    payload = response.json()
+    assert "sort" in payload["errors"]
+
+
+@pytest.mark.django_db
+def test_players_api_returns_400_for_invalid_range_combination(client):
+    response = client.get(reverse("api:players"), data={"age_min": 30, "age_max": 20})
+    assert response.status_code == 400
+    payload = response.json()
+    assert "age_max" in payload["errors"]