feat(mazenet): repo methods for topology/LAN/decky/edge/status events

Adds topology CRUD to BaseRepository (NotImplementedError defaults) and
implements them in SQLModelRepository: create/get/list/delete topologies,
add/update/list LANs and TopologyDeckies, add/list edges, plus an atomic
update_topology_status that appends a TopologyStatusEvent in the same
transaction.  Cascade delete sweeps children before the topology row.

Covered by tests/topology/test_repo.py (roundtrip, per-topology name
uniqueness, status event log, cascade delete, status filter) and an
extension to tests/test_base_repo.py for the NotImplementedError surface.

tests/test_base_repo.py

@@ -88,6 +88,20 @@ async def test_base_repo_coverage():
         (dr.upsert_decky_shard, ({},)),
         (dr.list_decky_shards, ()),
         (dr.delete_decky_shards_for_host, ("u",)),
+        (dr.create_topology, ({},)),
+        (dr.get_topology, ("t",)),
+        (dr.list_topologies, ()),
+        (dr.update_topology_status, ("t", "active")),
+        (dr.delete_topology_cascade, ("t",)),
+        (dr.add_lan, ({},)),
+        (dr.update_lan, ("l", {})),
+        (dr.list_lans_for_topology, ("t",)),
+        (dr.add_topology_decky, ({},)),
+        (dr.update_topology_decky, ("d", {})),
+        (dr.list_topology_deckies, ("t",)),
+        (dr.add_topology_edge, ({},)),
+        (dr.list_topology_edges, ("t",)),
+        (dr.list_topology_status_events, ("t",)),
     ]:
         with pytest.raises(NotImplementedError):
             await coro(*args)