fix inconsistent error code

server/mergin/sync/public_api_v2_controller.py

@@ -351,9 +351,8 @@ def create_project_version(id):
         if ProjectVersion.query.filter_by(
             project_id=project.id, name=next_version
         ).count():
-            return UploadError(
-                error=f"Version {v_next_version} already exists"
-            ).response(409)
+            upload.clear()
+            return ProjectVersionExists(version, next_version).response(409)
         move_to_tmp(version_dir)
 
     try:

server/mergin/tests/test_public_api_v2.py

@@ -1108,6 +1108,14 @@ def test_create_version_failures(client):
         response = client.post(f"v2/projects/{project.id}/versions", json=data)
         assert response.status_code == 409
 
+    # target version already exists on server (both on disk and in db), upload is released
+    with patch.object(Project, "next_version", return_value=1):
+        response = client.post(f"v2/projects/{project.id}/versions", json=data)
+        assert response.status_code == 409
+        assert response.json["code"] == ProjectVersionExists.code
+        assert not Upload.query.filter_by(project_id=project.id).first()
+        assert project.latest_version == 1
+
 
 def test_create_version_permanent_error_takes_priority(client):
     """Permanent errors (e.g. storage limit) must be reported before a