fix(topology): stop infinite render loop crashing the Topology page (#37) (#39)

The Topology page crashed on load with React error #185 ("Maximum update
depth exceeded"), thrown from inside React Flow's setNodes.

Root cause: handleDeleteManual depended on the whole TanStack Query
useMutation result object, which is recreated on every render. That made
handleDeleteManual unstable, which made the `graph` useMemo recompute every
render, which made the node/edge sync effect fire every render — calling
setNodes/setEdges in a loop until React aborted.

Fix: depend on the referentially-stable `.mutate` function instead of the
whole mutation object, so handleDeleteManual stays stable and `graph` only
rebuilds when the underlying data or connectMode actually change.

Verified: tsc --noEmit clean, eslint clean, vite build succeeds, and the
Topology page renders without #185 in a local Docker build.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/pages/TopologyPage.tsx

@@ -516,10 +516,17 @@ export default function TopologyPage() {
     onSuccess: () => queryClient.invalidateQueries({ queryKey: ['topology'] }),
   });
 
+  // Depend on the stable `.mutate` function rather than the whole mutation object.
+  // TanStack Query recreates the mutation result object on every render but keeps
+  // `.mutate` referentially stable, so this keeps handleDeleteManual stable too.
+  // Depending on the whole object would make handleDeleteManual — and therefore the
+  // `graph` memo and the node/edge sync effect below — re-run on every render,
+  // causing an infinite setNodes/setEdges loop (React error #185).
+  const deleteManualLinkMutate = deleteManualLinkMutation.mutate;
   const handleDeleteManual = useCallback((edgeId: string) => {
     const id = parseInt(edgeId);
-    if (!isNaN(id)) deleteManualLinkMutation.mutate(id);
+    if (!isNaN(id)) deleteManualLinkMutate(id);
-  }, [deleteManualLinkMutation]);
+  }, [deleteManualLinkMutate]);
 
   const [nodes, setNodes, onNodesChange] = useNodesState<Node>([]);
   const [edges, setEdges, onEdgesChange] = useEdgesState<Edge>([]);