fix(events): keep registration status reads nonblocking

apps/events/migrations/0018_registrationnotification_reg_notif_pending_idx.py

@@ -0,0 +1,17 @@
+# Generated by Django 5.2.5 on 2026-10-01 09:49
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('events', '0017_registrationnotification'),
+    ]
+
+    operations = [
+        migrations.AddIndex(
+            model_name='registrationnotification',
+            index=models.Index(condition=models.Q(('delivered_at__isnull', True)), fields=['lease_until', 'created_at'], name='reg_notif_pending_idx'),
+        ),
+    ]