feat: duration vs cost scatter plot tab (Task C.3)

dash_app/callbacks/chart.py

@@ -317,6 +317,31 @@ def _render_depth(app_state, title):
     return create_pathway_depth_figure(data, title)
 
 
+def _render_scatter(app_state, title):
+    """Build the duration vs cost scatter plot from current filter state."""
+    from dash_app.data.queries import get_duration_cost_scatter
+    from visualization.plotly_generator import create_duration_cost_scatter_figure
+
+    filter_id = (app_state or {}).get("date_filter_id", "all_6mo")
+    chart_type = (app_state or {}).get("chart_type", "directory")
+
+    selected_dirs = (app_state or {}).get("selected_directorates") or []
+    selected_trusts = (app_state or {}).get("selected_trusts") or []
+    directory = selected_dirs[0] if len(selected_dirs) == 1 else None
+    trust = selected_trusts[0] if len(selected_trusts) == 1 else None
+
+    try:
+        data = get_duration_cost_scatter(filter_id, chart_type, directory, trust)
+    except Exception:
+        log.exception("Failed to load duration/cost scatter data")
+        return _empty_figure("Failed to load scatter data.")
+
+    if not data:
+        return _empty_figure("No duration/cost data available.\nTry adjusting your filters.")
+
+    return create_duration_cost_scatter_figure(data, title)
+
+
 def register_chart_callbacks(app):
     """Register tab switching, pathway data loading, and chart rendering callbacks."""
 
@@ -463,6 +488,9 @@ def register_chart_callbacks(app):
         elif active_tab == "depth":
             fig = _render_depth(app_state, title)
 
+        elif active_tab == "scatter":
+            fig = _render_scatter(app_state, title)
+
         else:
             # Placeholder for charts not yet implemented
             tab_label = dict(TAB_DEFINITIONS).get(active_tab, active_tab)