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_validate.py

@@ -162,7 +162,7 @@ async def test_deploy_aborts_on_validation_error(repo, tmp_path, monkeypatch):
     from sqlmodel import select
     from decnet.web.db.models import LAN
     async with repo._session() as s:
-        row = (await s.execute(select(LAN).where(LAN.id == lan["id"]))).scalar_one()
+        row = (await s.execute(select(LAN).where(LAN.id == lan.id))).scalar_one()
         row.is_dmz = False
         s.add(row)
         await s.commit()
@@ -176,7 +176,7 @@ async def test_deploy_aborts_on_validation_error(repo, tmp_path, monkeypatch):
             await deploy_topology(repo, tid)
 
     topo = await repo.get_topology(tid)
-    assert topo["status"] == TopologyStatus.PENDING
+    assert topo.status == TopologyStatus.PENDING
 
 
 # --------------------------------------------------------------------- gateway-in-dmz