feat(events): harden registration checkout lifecycle

apps/payments/migrations/0007_payment_gateway_paid_at.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.2.5 on 2026-10-01 04:42
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('payments', '0006_payment_refund_attempts_and_more'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='payment',
+            name='gateway_paid_at',
+            field=models.DateTimeField(blank=True, editable=False, null=True),
+        ),
+    ]