feat(events): harden registration checkout lifecycle

apps/events/migrations/0016_registration_cancellation_reason_and_more.py

@@ -0,0 +1,28 @@
+# Generated by Django 5.2.5 on 2026-09-30 19:44
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('events', '0015_registration_attendance_verification_source_and_more'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='registration',
+            name='cancellation_reason',
+            field=models.CharField(blank=True, choices=[('checkout_expired', 'Checkout expired'), ('user_cancelled', 'User cancelled checkout'), ('event_cancelled', 'Event cancelled'), ('payment_failed', 'Payment failed')], default='', editable=False, max_length=32),
+        ),
+        migrations.AddField(
+            model_name='registration',
+            name='checkout_expires_at',
+            field=models.DateTimeField(blank=True, editable=False, null=True),
+        ),
+        migrations.AddField(
+            model_name='registration',
+            name='checkout_started_at',
+            field=models.DateTimeField(blank=True, editable=False, null=True),
+        ),
+    ]