Add choices constraint to cluster_mode in ClusterSettings model

cluster/migrations/0004_alter_clustersettings_cluster_mode.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.2.9 on 2025-12-29 20:00
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('cluster', '0003_workerstatus_wireguard_status'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='clustersettings',
+            name='cluster_mode',
+            field=models.CharField(choices=[('mirror', 'Mirror')], default='mirror', max_length=16),
+        ),
+    ]