fix: retry transient official source failures

backend/tests/test_sprint181_mol_municipality_workspace.py

@@ -85,6 +85,17 @@ def test_mol_provisioner_refuses_a_truncated_municipality_dataset() -> None:
         module.build_municipality_buildings(pages, boundary, max_features=1)
 
 
+def test_mol_source_session_retries_only_safe_get_requests() -> None:
+    module = load_provisioner()
+
+    with module.build_source_session() as session:
+        retry = session.get_adapter("https://").max_retries
+
+    assert retry.total == 5
+    assert retry.allowed_methods == frozenset({"GET"})
+    assert set(retry.status_forcelist) == {429, 500, 502, 503, 504}
+
+
 def test_large_vector_persistence_flushes_once_without_per_feature_refresh() -> None:
     class FakeSession:
         def __init__(self) -> None: