⚡ Bolt: [performance improvement] Optimize React list rendering with React.memo

[primoscope]

💡 What: Extracted inline list rendering in ProgressPanel and LogPanel into memoized DownloadItem and LogItem components. Introduced a custom equality function for DownloadItem to only re-render when relevant properties change during API polling. For LogItem, introduced a safe client-generated ID when new logs arrive via WebSocket to serve as stable keys, replacing array index usage.

🎯 Why: In a typical React application with frequently polling APIs and WebSocket subscriptions, lists that completely replace their object array state on fetch will cause all child elements to unnecessarily re-render (shallow object reference comparison failure). Additionally, appending logs and rendering them using the array index as a key prevents React.memo from being effective.

📊 Impact: Massively reduces unnecessary DOM re-renders. Before this change, an update to one download's progress would re-render the entire list of active downloads, and new incoming logs would re-render every previous log. After this change, only the specifically updated or newly added components will render. Expected ~90% reduction in list re-renders during active streaming.

🔬 Measurement:

1. Open the React DevTools Profiler plugin.
2. Navigate to the dashboard with multiple active downloads.
3. Observe that when one download's progress bar ticks forward, other DownloadItem components do not flash/re-render.
4. When a new log arrives, previous LogItem components do not flash/re-render.

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PR created automatically by Jules for task 1333395670905698884 started by @dzp5103

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