changed payment code to demo code

backend/core/migrations/0018_rename_paymentcode_democode.py

@@ -0,0 +1,17 @@
+# Generated by Django 5.1.3 on 2025-07-13 22:45
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0017_document_key_findings'),
+    ]
+
+    operations = [
+        migrations.RenameModel(
+            old_name='PaymentCode',
+            new_name='DemoCode',
+        ),
+    ]