Implement historical tracking using django-pghistory; add middleware for context capture and update model architecture

memory-bank/features/history-visualization.md

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+## Feature: Unified History Timeline (HTMX Integrated)
+
+### HTMX Template Pattern
+```django
+{# history/partials/history_timeline.html #}
+<div id="history-timeline" 
+     hx-get="{% url 'history:timeline' content_type_id=content_type.id object_id=object.id %}"
+     hx-trigger="every 30s, historyUpdate from:body">
+  <div class="space-y-4">
+    {% for event in events %}
+      <div class="component-wrapper bg-white p-4 shadow-sm">
+        <div class="component-header flex items-center gap-2 mb-2">
+          <span class="text-sm font-medium">{{ event.pgh_label|title }}</span>
+          <time class="text-xs text-gray-500">{{ event.pgh_created_at|date:"M j, Y H:i" }}</time>
+        </div>
+        <div class="component-content text-sm">
+          {% if event.pgh_context.metadata.user %}
+            <div class="flex items-center gap-1">
+              <svg class="w-4 h-4">...</svg>
+              <span>{{ event.pgh_context.metadata.user }}</span>
+            </div>
+          {% endif %}
+        </div>
+      </div>
+    {% endfor %}
+  </div>
+</div>
+```
+
+### View Integration (Class-Based with HTMX)
+```python
+# history/views.py
+class HistoryTimelineView(View):
+    def get(self, request, content_type_id, object_id):
+        events = ModelHistory.objects.filter(
+            pgh_obj_model=content_type_id,
+            pgh_obj_id=object_id
+        ).order_by('-pgh_created_at')[:25]
+
+        if request.htmx:
+            return render(request, "history/partials/history_timeline.html", {
+                "events": events
+            })
+            
+        return JsonResponse({
+            'history': [serialize_event(e) for e in events]
+        })
+```
+
+### Event Trigger Pattern
+```python
+# parks/signals.py
+from django.dispatch import Signal
+history_updated = Signal()
+
+# In model save/delete handlers:
+history_updated.send(sender=Model, instance=instance)