Eliminate N+1 queries in workflow visualization controller

app/controllers/discourse_workflow/workflow_visualisation_controller.rb

@@ -16,32 +16,48 @@ def network
         # Preload steps + options (and their workflow_option) to avoid extra queries when iterating
         steps = workflow.workflow_steps.order(:position).includes(workflow_step_options: :workflow_option)
 
+        # Build a hash of category_id => category to avoid N+1 queries
+        category_ids = steps.filter_map(&:category_id).uniq
+        categories_by_id = Category.where(id: category_ids).index_by(&:id)
+
+        # Build a hash of step_id => step for quick lookups in links
+        steps_by_id = steps.index_by(&:id)
+
         # Lanes: unique categories in order of step position
         lanes = steps.map do |step|
-          category = Category.find(step.category_id)
+          category = categories_by_id[step.category_id]
+          next unless category
+
           {
             name: category.name,
             link: "/c/#{step.category_id}"
           }
-        end.uniq { |lane| lane[:name] }
+        end.compact.uniq { |lane| lane[:name] }
+
+        # Build lane name to index hash for efficient lookups
+        lane_index_by_name = lanes.each_with_index.to_h { |lane, idx| [lane[:name], idx] }
 
         # Nodes: one per step
         nodes = steps.map do |step|
-          category_name = Category.find(step.category_id).name
+          category = categories_by_id[step.category_id]
+          next unless category
+
+          category_name = category.name
 
           {
             id: step.name,
-            lane: lanes.find_index { |lane| lane[:name] == category_name },
+            lane: lane_index_by_name[category_name],
             active: step.id == workflow_state.workflow_step_id
           }
-        end
+        end.compact
 
         # Links: from each step via its options
         links = []
 
         steps.each do |step|
           step.workflow_step_options.each do |option|
-            target_step = DiscourseWorkflow::WorkflowStep.find(option.target_step_id)
+            target_step = steps_by_id[option.target_step_id]
+            next unless target_step
 
             links << {
               source: step.name,