fix(accounts): add merge migration to resolve conflicting eventify_id migrations

0011_user_eventify_id and 0012_user_eventify_id both added eventify_id field
from different base migrations. Created 0013 merge node to unify the graph.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

accounts/migrations/0013_merge_eventify_id.py

@@ -0,0 +1,13 @@
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+    """Merge migration to resolve conflicting eventify_id migrations."""
+
+    dependencies = [
+        ('accounts', '0011_user_eventify_id'),
+        ('accounts', '0012_user_eventify_id'),
+    ]
+
+    operations = [
+    ]