refactor(topology): introduce TopologyRepository protocol with DTO return types

Replace repo: BaseRepository with a structural TopologyRepository protocol
in persistence.py and allocator.py. All read methods now return typed DTOs
(TopologySummary, LANRow, DeckyRow, EdgeRow) instead of raw dicts, eliminating
silent field-shape regressions across the topology subsystem.

TopologySummary gains email_personas and language_default so api_personas.py
can continue reading those fields via attribute access. hydrate() converts
DTOs to dicts before passing to _backfill_decky_configs, keeping the mutable
working-state function dict-based at its boundary. All production callers
(router handlers, mutator, CLI, heartbeat) migrated from dict/get access to
attribute access. 134 tests pass.

decnet/cli/topology.py

@@ -233,8 +233,8 @@ def _delete(
         topo = await repo.get_topology(topology_id)
         if topo is None:
             return False, "not-found"
-        if topo["status"] in _RUNNING:
-            return False, str(topo["status"])
+        if topo.status in _RUNNING:
+            return False, str(topo.status)
         ok = await repo.delete_topology_cascade(topology_id)
         return ok, None