⚡ Bolt: [performance improvement] Pre-index nodes for faster graph search

[hadsern]

💡 What: Optimized search arrays in KnowledgeGraph.tsx by pre-indexing nodes into an exactMap and a searchList array of pre-lowercased strings.
🎯 Why: To eliminate redundant string operations (toLowerCase()) running within useMemo loops and event handler arrays, which causes high CPU overhead when typing/searching on large datasets.
📊 Impact: Reduces re-calculation complexity. O(1) time complexity for exact lookups and significant performance improvement during partial search loops by skipping .toLowerCase() evaluation on all elements.
🔬 Measurement: By typing in the graph filter input, re-renders and CPU processing time on keydown are reduced.

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PR created automatically by Jules for task 9518882935255554192 started by @hadsern

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