feat: add two-view architecture with sidebar navigation (Task 10.2)

- Add active_view and selected_comparison_directorate to app-state
- Sidebar: rename to Patient Pathways + add Trust Comparison nav item
- View container pattern: two view divs toggled by active_view
- Navigation callback: sidebar clicks switch views + update active state
- Trust Comparison placeholder landing page with tc-landing structure

dash_app/callbacks/__init__.py

@@ -7,8 +7,10 @@ def register_callbacks(app):
     from dash_app.callbacks.chart import register_chart_callbacks
     from dash_app.callbacks.kpi import register_kpi_callbacks
     from dash_app.callbacks.modals import register_modal_callbacks
+    from dash_app.callbacks.navigation import register_navigation_callbacks
 
     register_filter_callbacks(app)
     register_chart_callbacks(app)
     register_kpi_callbacks(app)
     register_modal_callbacks(app)
+    register_navigation_callbacks(app)

dash_app/callbacks/filters.py

@@ -73,13 +73,15 @@ def register_filter_callbacks(app):
         Input("filter-last-seen", "value"),
         Input("all-drugs-chips", "value"),
         Input("trust-chips", "value"),
+        Input("nav-patient-pathways", "n_clicks"),
+        Input("nav-trust-comparison", "n_clicks"),
         State("app-state", "data"),
     )
     def update_app_state(
         _dir_clicks, _ind_clicks, initiated, last_seen, selected_drugs,
-        selected_trusts, current_state
+        selected_trusts, _nav_pp_clicks, _nav_tc_clicks, current_state
     ):
-        """Update app-state when chart type toggle, date filters, drug chips, or trust chips change."""
+        """Update app-state when chart type toggle, date filters, drug/trust chips, or sidebar nav change."""
         if not current_state:
             current_state = {
                 "chart_type": "directory",
@@ -89,6 +91,8 @@ def register_filter_callbacks(app):
                 "selected_drugs": [],
                 "selected_directorates": [],
                 "selected_trusts": [],
+                "active_view": "patient-pathways",
+                "selected_comparison_directorate": None,
             }
 
         triggered_id = ctx.triggered_id
@@ -100,6 +104,13 @@ def register_filter_callbacks(app):
         elif triggered_id == "chart-type-indication":
             chart_type = "indication"
 
+        # Determine active view from sidebar nav
+        active_view = current_state.get("active_view", "patient-pathways")
+        if triggered_id == "nav-patient-pathways":
+            active_view = "patient-pathways"
+        elif triggered_id == "nav-trust-comparison":
+            active_view = "trust-comparison"
+
         # Compute date_filter_id from dropdown values
         date_filter_id = f"{initiated}_{last_seen}"
 
@@ -112,12 +123,13 @@ def register_filter_callbacks(app):
             "date_filter_id": date_filter_id,
             "selected_drugs": selected_drugs or [],
             "selected_trusts": selected_trusts or [],
+            "active_view": active_view,
         }
 
         # Toggle pill CSS classes
         base = "toggle-pill"
-        active = f"{base} toggle-pill--active"
-        dir_class = active if chart_type == "directory" else base
-        ind_class = active if chart_type == "indication" else base
+        active_cls = f"{base} toggle-pill--active"
+        dir_class = active_cls if chart_type == "directory" else base
+        ind_class = active_cls if chart_type == "indication" else base
 
         return updated_state, dir_class, ind_class

dash_app/callbacks/navigation.py

@@ -0,0 +1,29 @@
+"""Callbacks for view switching between Patient Pathways and Trust Comparison."""
+from dash import Input, Output
+
+
+def register_navigation_callbacks(app):
+    """Register view switching callbacks."""
+
+    @app.callback(
+        Output("patient-pathways-view", "style"),
+        Output("trust-comparison-view", "style"),
+        Output("nav-patient-pathways", "className"),
+        Output("nav-trust-comparison", "className"),
+        Input("app-state", "data"),
+    )
+    def switch_view(app_state):
+        """Show/hide views and update sidebar active state based on active_view."""
+        if not app_state:
+            return {}, {"display": "none"}, "sidebar__item sidebar__item--active", "sidebar__item"
+
+        view = app_state.get("active_view", "patient-pathways")
+        show = {}
+        hide = {"display": "none"}
+        active_cls = "sidebar__item sidebar__item--active"
+        inactive_cls = "sidebar__item"
+
+        if view == "patient-pathways":
+            return show, hide, active_cls, inactive_cls
+        else:
+            return hide, show, inactive_cls, active_cls