Add test utilities and state machine diagrams for FSM models

- Introduced reusable test utilities in `backend/tests/utils` for FSM transitions, HTMX interactions, and common scenarios.
- Added factory functions for creating test submissions, parks, rides, and photo submissions.
- Implemented assertion helpers for verifying state changes, toast notifications, and transition logs.
- Created comprehensive state machine diagrams for all FSM-enabled models in `docs/STATE_DIAGRAMS.md`, detailing states, transitions, and guard conditions.

backend/apps/moderation/views.py

@@ -18,6 +18,8 @@ from django_filters.rest_framework import DjangoFilterBackend
 from django.contrib.auth import get_user_model
 from django.utils import timezone
 from django.db.models import Q, Count
+from django.shortcuts import render
+from django.core.paginator import Paginator
 from datetime import timedelta
 from django_fsm import can_proceed, TransitionNotAllowed
 
@@ -334,31 +336,85 @@ class ModerationReportViewSet(viewsets.ModelViewSet):
 
     @action(detail=False, methods=['get'], permission_classes=[CanViewModerationData])
     def all_history(self, request):
-        """Get all transition history with filtering."""
+        """Get all transition history with filtering.
+
+        Supports both HTMX (returns HTML partials) and API (returns JSON) requests.
+        """
         from django_fsm_log.models import StateLog
         from django.contrib.contenttypes.models import ContentType
-        
+
         queryset = StateLog.objects.select_related('by', 'content_type').all()
 
         # Filter by id (for detail view)
         log_id = request.query_params.get('id')
         if log_id:
-            queryset = queryset.filter(id=log_id)
+            try:
+                log = queryset.get(id=log_id)
+                # Check if HTMX request for detail view
+                if request.headers.get('HX-Request'):
+                    return render(request, 'moderation/partials/history_detail_content.html', {
+                        'log': log,
+                    })
+                # Return JSON for API request
+                return Response({
+                    'id': log.id,
+                    'timestamp': log.timestamp,
+                    'model': log.content_type.model,
+                    'object_id': log.object_id,
+                    'state': log.state,
+                    'from_state': log.source_state,
+                    'to_state': log.state,
+                    'transition': log.transition,
+                    'user': log.by.username if log.by else None,
+                    'description': log.description,
+                    'reason': log.description,
+                })
+            except StateLog.DoesNotExist:
+                if request.headers.get('HX-Request'):
+                    return render(request, 'moderation/partials/history_detail_content.html', {
+                        'log': None,
+                    })
+                return Response({'error': 'Log not found'}, status=status.HTTP_404_NOT_FOUND)
 
-        # Filter by model type
+        # Filter by model type with app_label support for correct ContentType resolution
         model_type = request.query_params.get('model_type')
+        app_label = request.query_params.get('app_label')
         if model_type:
             try:
-                content_type = ContentType.objects.get(model=model_type)
+                if app_label:
+                    # Use both app_label and model for precise matching
+                    content_type = ContentType.objects.get_by_natural_key(app_label, model_type)
+                else:
+                    # Map common model names to their app_labels for correct resolution
+                    model_app_mapping = {
+                        'park': 'parks',
+                        'ride': 'rides',
+                        'editsubmission': 'submissions',
+                        'photosubmission': 'submissions',
+                        'moderationreport': 'moderation',
+                        'moderationqueue': 'moderation',
+                        'bulkoperation': 'moderation',
+                    }
+                    mapped_app_label = model_app_mapping.get(model_type.lower())
+                    if mapped_app_label:
+                        content_type = ContentType.objects.get_by_natural_key(mapped_app_label, model_type.lower())
+                    else:
+                        # Fallback to model-only lookup
+                        content_type = ContentType.objects.get(model=model_type)
                 queryset = queryset.filter(content_type=content_type)
             except ContentType.DoesNotExist:
                 pass
-        
+
+        # Filter by object_id (for object-level history)
+        object_id = request.query_params.get('object_id')
+        if object_id:
+            queryset = queryset.filter(object_id=object_id)
+
         # Filter by user
         user_id = request.query_params.get('user_id')
         if user_id:
             queryset = queryset.filter(by_id=user_id)
-        
+
         # Filter by date range
         start_date = request.query_params.get('start_date')
         end_date = request.query_params.get('end_date')
@@ -366,16 +422,41 @@ class ModerationReportViewSet(viewsets.ModelViewSet):
             queryset = queryset.filter(timestamp__gte=start_date)
         if end_date:
             queryset = queryset.filter(timestamp__lte=end_date)
-        
+
         # Filter by state
         state = request.query_params.get('state')
         if state:
             queryset = queryset.filter(state=state)
-        
+
+        # Search filter (case-insensitive across relevant fields)
+        search_query = request.query_params.get('q')
+        if search_query:
+            queryset = queryset.filter(
+                Q(transition__icontains=search_query) |
+                Q(description__icontains=search_query) |
+                Q(state__icontains=search_query) |
+                Q(source_state__icontains=search_query) |
+                Q(object_id__icontains=search_query) |
+                Q(by__username__icontains=search_query)
+            )
+
         # Order queryset
         queryset = queryset.order_by('-timestamp')
 
-        # Paginate
+        # Check if HTMX request
+        if request.headers.get('HX-Request'):
+            # Use Django's Paginator for HTMX responses
+            paginator = Paginator(queryset, 20)
+            page_number = request.query_params.get('page', 1)
+            page_obj = paginator.get_page(page_number)
+
+            return render(request, 'moderation/partials/history_table.html', {
+                'history_logs': page_obj,
+                'page_obj': page_obj,
+                'request': request,
+            })
+
+        # Paginate for API response
         page = self.paginate_queryset(queryset)
         if page is not None:
             history_data = [{