⚡ Bolt: [performance improvement] Optimize high-frequency WebSocket list rendering

[primoscope]

💡 What:

• Extracted DownloadItem and LogItem into separate React.memo components in ProgressPanel.tsx and LogPanel.tsx.
• Provided a custom primitive-checking equality function for DownloadItem to accurately handle continuous API/WebSocket polling states.
• Replaced array-index keys in LogPanel with stable, client-generated IDs (Date.now() + Math.random()).
• Moved purely static helper functions (formatSpeed, getLogColor, etc.) outside of component bodies to avoid unnecessary functional recreation.

🎯 Why:
During active downloads, the backend emits high-frequency WebSocket events (progress updates, logs). Previously, these updates triggered O(N) re-renders across all items in the DOM list, which is a known React performance bottleneck, especially on lower-end devices processing many simultaneous downloads or dense log streams.

📊 Impact:
Reduces re-renders significantly. Modifying an individual download's progress now only re-renders that specific DownloadItem rather than the entire ProgressPanel list. Log additions only render the new LogItem rather than reconciling the entire array.

🔬 Measurement:

1. Start multiple concurrent downloads on the frontend.
2. Open React Developer Tools Profiler.
3. Observe that only individual items re-render upon receiving granular progress/speed WebSocket updates, instead of the parent container and all sibling nodes.

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PR created automatically by Jules for task 1409171786966458325 started by @dzp5103

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