fix(selection): render gold brick chart as TDX brick blocks with strong-red flag

Match the ZXB1 sub-chart formula: each brick spans between yesterday's
and today's brick value via a stacked range bar — rising bricks are
hollow red (solid on strong_red), falling bricks solid green. The chart
API now also returns brick_strong_red per point.

zhixing-server/tests/test_selection_http.py

@@ -141,6 +141,7 @@ class FakeChartService:
                     trend_white=10.2,
                     trend_yellow=10.4,
                     brick_chart=5.0 if include_brick_chart else None,
+                    brick_strong_red=True if include_brick_chart else None,
                 ),
             ),
         )
@@ -462,6 +463,7 @@ def test_chart_returns_bounded_qfq_contract() -> None:
                 "trend_white": 10.2,
                 "trend_yellow": 10.4,
                 "brick_chart": None,
+                "brick_strong_red": None,
             }
         ],
     }
@@ -478,6 +480,7 @@ def test_chart_requests_brick_series_for_gold_brick_strategy() -> None:
     assert response.status_code == 200
     assert chart_service.request == ("000001.SZ", TARGET, True)
     assert response.json()["points"][0]["brick_chart"] == 5.0
+    assert response.json()["points"][0]["brick_strong_red"] is True
 
 
 @pytest.mark.parametrize(