feat(mazenet): persist canvas layout per topology to localStorage

Dragging a LAN or decky, or resizing a NetBox, updates React state
but previously vanished on reload because the grid-layout adapter
rewrote everything from the graph. Add a per-topology localStorage
snapshot (key: mazenet.layout.<topologyId>) that captures net
x/y/w/h and decky x/y; useLayoutPersistor writes it debounced, and
getTopology merges it over adaptTopology's grid so entities without
a stored entry still fall back to a clean auto-layout. Deleting a
topology calls clearLayout to drop its snapshot.

decnet_web/src/components/MazeNET/useMazeApi.ts

@@ -3,6 +3,7 @@ import api from '../../utils/api';
 import { ARCHETYPES as DEFAULT_ARCHETYPES, DEFAULT_SERVICES } from './data';
 import type { Archetype, ServiceDef } from './data';
 import type { Net, MazeNode, Edge, DeckyNode } from './types';
+import { applyLayout, loadLayout } from './useMazeLayoutStore';
 
 export interface LANRow {
   id: string;
@@ -214,7 +215,10 @@ export function useMazeApi(): MazeApi {
 
   const getTopology = useCallback(async (id: string) => {
     const { data } = await api.get<TopologyDetail>(`/topologies/${id}`);
-    return adaptTopology(data);
+    const hydrated = adaptTopology(data);
+    const layout = loadLayout(id);
+    const { nets, nodes } = applyLayout(hydrated.nets, hydrated.nodes, layout);
+    return { ...hydrated, nets, nodes };
   }, []);
 
   const getServices = useCallback(async () => {