Moves the 31 MazeNET topology methods (topologies CRUD, LANs, deckies,
edges, status events, mutation queue) into sqlmodel_repo/topology.py.
Includes _assert_pending and _check_and_bump_version concurrency
guards.
This is the last domain extraction; sqlmodel_repo/__init__.py is now
~165 lines: lifecycle (initialize/reinitialize/migrations), the admin
self-heal seed, get_state/set_state, and the mixin composition.
