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/unit/selection/test_chart.py

@@ -127,10 +127,15 @@ def test_chart_skips_brick_series_by_default_and_computes_on_request() -> None:
             "volume": [bar.volume for bar in history.bars],
         }
     )
-    expected = prepare_gold_brick_indicators(frame, history.ts_code)["brick_chart"]
-    assert brick_chart.points[-1].brick_chart == pytest.approx(float(expected.iloc[-1]))
+    prepared = prepare_gold_brick_indicators(frame, history.ts_code)
+    assert brick_chart.points[-1].brick_chart == pytest.approx(
+        float(prepared["brick_chart"].iloc[-1])
+    )
+    assert brick_chart.points[-1].brick_strong_red is bool(prepared["strong_red"].iloc[-1])
     assert brick_chart.points[0].trade_date == history.bars[10].trade_date
-    assert brick_chart.points[0].brick_chart == pytest.approx(float(expected.iloc[10]))
+    assert brick_chart.points[0].brick_chart == pytest.approx(
+        float(prepared["brick_chart"].iloc[10])
+    )
 
 
 def test_chart_rejects_empty_history() -> None: