Add user_login field and migrate existing credentials.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/apps/accounts/migrations/0012_user_login.py

@@ -0,0 +1,32 @@
+from django.db import migrations, models
+
+
+def copy_user_name_to_user_login(apps, schema_editor):
+    User = apps.get_model("accounts", "User")
+    for user in User.objects.all():
+        user.user_login = user.user_name
+        user.save(update_fields=["user_login"])
+
+
+def noop_reverse(apps, schema_editor):
+    pass
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("accounts", "0011_superuser_status"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="user",
+            name="user_login",
+            field=models.CharField(max_length=30, null=True),
+        ),
+        migrations.RunPython(copy_user_name_to_user_login, noop_reverse),
+        migrations.AlterField(
+            model_name="user",
+            name="user_login",
+            field=models.CharField(max_length=30, unique=True),
+        ),
+    ]