Fix Chart Update

[MaddieWright]

What?

Improved the Chart View node's graph and data table for better EEG signal readability.

• Y-axis now auto-scales to actual signal range (µV) with labeled axis and 50 tick marks
• Replaced yellow Signal 4 colour with red for visibility
• Added a scrollable Brush component on the X-axis so users can pan through buffered data without losing their scroll position across start/stop cycles
• Added a display info bar showing buffered point count, visible time window, and full time range
• Data table now shows last 50 rows with an "Expand full table" dialog to view all buffered data points
• Fixed timestamp formatting to support sub-second precision (HH:MM:SS.mmm) for both ISO 8601 and space-separated formats
• Increased chart data buffer from 20 to 500 points so the table and chart have enough data to render

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How?

• signal-graph-full.tsx: Added Recharts Brush with controlled startIndex/endIndex state that persists across re-renders; brush position is preserved on stream stop/start and only resets when brushRange state is cleared. Display info bar computes visible sample count dynamically from brush indices. Table uses a Dialog for the expanded view.
• signal-graph-node.tsx: Bumped useNodeData chartSize from 20 → 500.
• WebSocketContext.tsx: Updated formatTimestamp to handle space-separated timestamps and extract milliseconds.
• data-table.tsx: Added rowCount prop (was hardcoded to 8).