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/topology/repository.py

@@ -0,0 +1,29 @@
+from __future__ import annotations
+
+from typing import Any, Optional, Protocol
+
+from decnet.web.db.models.topology import DeckyRow, EdgeRow, LANRow, TopologySummary
+
+
+class TopologyRepository(Protocol):
+    """Structural contract for the topology subsystem's repo dependency.
+
+    Declares only the 10 methods the topology package actually calls.
+    Any object with matching async signatures satisfies this Protocol
+    without inheritance — including BaseRepository and test stubs.
+    """
+
+    async def create_topology(self, data: dict[str, Any]) -> str: ...
+    async def get_topology(self, topology_id: str) -> Optional[TopologySummary]: ...
+    async def update_topology_status(
+        self, topology_id: str, new_status: str, reason: Optional[str] = None
+    ) -> None: ...
+    async def list_topologies(
+        self, status: Optional[str] = None
+    ) -> list[TopologySummary]: ...
+    async def add_lan(self, data: dict[str, Any]) -> str: ...
+    async def list_lans_for_topology(self, topology_id: str) -> list[LANRow]: ...
+    async def add_topology_decky(self, data: dict[str, Any]) -> str: ...
+    async def list_topology_deckies(self, topology_id: str) -> list[DeckyRow]: ...
+    async def add_topology_edge(self, data: dict[str, Any]) -> str: ...
+    async def list_topology_edges(self, topology_id: str) -> list[EdgeRow]: ...