style: make Patient Pathways chart fill available viewport height (Task 11.3)

- Changed .main from min-height to height with overflow-y auto
- Added flex chain: #view-container → #patient-pathways-view → .chart-card
  → dcc.Loading wrapper → #chart-container → #pathway-chart
- All flex parents get min-height: 0 for proper flex shrinking
- dcc.Graph set to responsive=True with flex: 1 and minHeight: 0
- Trust Comparison view scrolls naturally via .main overflow-y auto

dash_app/components/chart_card.py

@@ -81,7 +81,8 @@ def make_chart_card():
                         children=[
                             dcc.Graph(
                                 id="pathway-chart",
-                                style={"minHeight": "500px", "flex": "1"},
+                                style={"flex": "1", "minHeight": "0"},
+                                responsive=True,
                                 config={
                                     "displayModeBar": True,
                                     "displaylogo": False,