Fix for category template creation (#11803)

- Prevent duplicate parameters
- Closes https://github.com/inventree/InvenTree/issues/11798

Co-authored-by: Copilot <copilot@github.com>

src/backend/InvenTree/part/models.py

@@ -2478,6 +2478,7 @@ class Part(
             category__in=categories
         ).order_by('-category__level')
 
+        template_ids = set()
         parameters = []
         content_type = ContentType.objects.get_for_model(Part)
 
@@ -2488,6 +2489,12 @@ class Part(
             ).exists():
                 continue
 
+            # Ensure we do not create duplicate parameters if multiple categories have the same template
+            if category_template.template.pk in template_ids:
+                continue
+
+            template_ids.add(category_template.template.pk)
+
             parameters.append(
                 Parameter(
                     template=category_template.template,
@@ -2497,7 +2504,6 @@ class Part(
                 )
             )
 
-        if len(parameters) > 0:
         Parameter.objects.bulk_create(parameters)
 
     def getTestTemplates(