fix(daemons): block owner transfer while assigned

tests/test_v1_portfolios_daemon_assignment.py

@@ -402,6 +402,20 @@ def test_patch_foreign_daemon_returns_404() -> None:
     assert resp.status_code == 404
 
 
+def test_patch_missing_daemon_returns_404_without_changing_portfolio() -> None:
+    repo = _repo_with_portfolio_and_daemons(owner=_USER_ID)
+    client = _make_client()
+
+    with _with_repo(repo):
+        resp = client.patch(
+            f"/v1/portfolios/{_PORTFOLIO_UUID}",
+            json={"managed_by_daemon_id": "ffffffff-ffff-ffff-ffff-ffffffffffff"},
+            headers=_auth("admin-tok"),
+        )
+    assert resp.status_code == 404
+    assert repo.get(_PORTFOLIO_UUID).managed_by_daemon_id is None
+
+
 def test_patch_inactive_daemon_returns_409() -> None:
     repo = _repo_with_portfolio_and_daemons(owner=_USER_ID, is_active=False)
     client = _make_client()
@@ -412,4 +426,4 @@ def test_patch_inactive_daemon_returns_409() -> None:
             json={"managed_by_daemon_id": _DAEMON_UUID},
             headers=_auth("admin-tok"),
         )
-    assert resp.status_code == 409
+    assert resp.status_code == 409