Return native Engine NotFound faults and clear Web UI session on 401.

Include the bad id in host/datacenter/cluster errors, expire stale auth in the
console, and document Ingress annotations that preserve fault bodies.

tests/unit/test_ovirt_common.py

@@ -0,0 +1,35 @@
+"""Unit tests for native Engine NotFound helpers."""
+
+from __future__ import annotations
+
+import pytest
+
+from app.ovirt.common import no_such
+from app.ovirt.errors import OVirtError, fault_body
+from app.ovirt.repr import generic_entity
+
+
+def test_no_such_includes_id_in_detail() -> None:
+    err = no_such("host", "pve01-bad-id")
+    assert isinstance(err, OVirtError)
+    assert err.status_code == 404
+    assert err.reason == "NotFound"
+    assert err.detail == "No such host ('pve01-bad-id')"
+
+
+def test_no_such_fault_body_is_json_not_html() -> None:
+    err = no_such("datacenter", "missing-dc")
+    body = fault_body(err, as_xml=False)
+    assert body == {
+        "fault": {"reason": "NotFound", "detail": "No such datacenter ('missing-dc')"}
+    }
+    xml = fault_body(err, as_xml=True)
+    assert isinstance(xml, str)
+    assert "No such datacenter ('missing-dc')" in xml
+    assert "<html" not in xml.lower()
+
+
+def test_generic_entity_none_raises_no_such() -> None:
+    with pytest.raises(OVirtError, match=r"No such host \('abc'\)") as caught:
+        generic_entity("hosts", "host", None, entity_id="abc")
+    assert caught.value.status_code == 404