fix: topology graph empty after async fetch

[reloadfast]

Root cause

useNodesState(initialNodes) and useEdgesState(initialEdges) from @xyflow/react only use their argument as the initial value at mount. The topology data is fetched asynchronously in a useEffect, so when React Flow initialised, both arrays were empty — and never updated when the fetch resolved.

There was an existing synced workaround (lines 216–222) that set a boolean flag but never called setNodes or setEdges, making it completely inert.

Fix

Capture setNodes and setEdges from the hooks and push updates via useEffect whenever initialNodes/initialEdges change:

const [rfNodes, setNodes, onNodesChange] = useNodesState(initialNodes);
const [rfEdges, setEdges, onEdgesChange] = useEdgesState(initialEdges);

useEffect(() => { setNodes(initialNodes); }, [initialNodes, setNodes]);
useEffect(() => { setEdges(initialEdges); }, [initialEdges, setEdges]);

Removes the dead synced state.

Testing

• 146 frontend tests pass
• ESLint + Prettier clean

Closes #109