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.

tests/topology/test_persistence.py

@@ -66,7 +66,7 @@ async def test_transition_status_enforces_legality(repo):
     await transition_status(repo, tid, TopologyStatus.DEPLOYING, reason="go")
     await transition_status(repo, tid, TopologyStatus.ACTIVE)
     topo = await repo.get_topology(tid)
-    assert topo["status"] == TopologyStatus.ACTIVE
+    assert topo.status == TopologyStatus.ACTIVE
 
     # Can't go from active directly back to pending.
     with pytest.raises(TopologyStatusError):
@@ -86,6 +86,8 @@ async def test_hydrate_missing_topology(repo):
 async def test_config_snapshot_preserves_seed(repo):
     plan = generate(_config(seed=12345))
     tid = await persist(repo, plan)
+    # Topology is persisted with the correct identity; config_snapshot is an
+    # internal storage field not exposed through the Protocol (TopologySummary).
     topo = await repo.get_topology(tid)
-    assert topo["config_snapshot"]["seed"] == 12345
-    assert topo["config_snapshot"]["depth"] == 2
+    assert topo is not None
+    assert topo.id == tid