Fix: correct doc version filename handling (#12223)

src/documents/migrations/0016_document_version_index_and_more.py

@@ -0,0 +1,37 @@
+# Generated by Django 5.2.11 on 2026-03-02 17:48
+
+from django.conf import settings
+from django.db import migrations
+from django.db import models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("documents", "0015_savedview_visibility_to_ui_settings"),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="document",
+            name="version_index",
+            field=models.PositiveIntegerField(
+                blank=True,
+                db_index=True,
+                help_text="Index of this version within the root document.",
+                null=True,
+                verbose_name="version index",
+            ),
+        ),
+        migrations.AddConstraint(
+            model_name="document",
+            constraint=models.UniqueConstraint(
+                condition=models.Q(
+                    ("root_document__isnull", False),
+                    ("version_index__isnull", False),
+                ),
+                fields=("root_document", "version_index"),
+                name="documents_document_root_version_index_uniq",
+            ),
+        ),
+    ]