feat: implement value history chart and volatility exposure meter

[petersdt]

Summary

Implemented the Value History chart tab in the Commitment Health Metrics section and added the Volatility Exposure meter as per design requirements.

Changes

• New Component: HealthMetricsValueHistoryChart.tsx to visualize commitment value changes over time.
• Updated Component: CommitmentHealthMetrics.tsx to support the new "Value History" tab and switching logic.
• Refactored Component: VolatilityExposureMeter (and CSS) to match the visual design (percent placement, gradient bar).
• Page Integration: Updated the Commitment Detail page to include both the new chart and the volatility exposure section with mock data.

Verification

• Navigate to http://localhost:3000/commitments/123
• Verify "Value History" tab is active by default and displays the chart with tooltips.
• Verify "Volatility Exposure" section appears below the chart with the correct gradient and layout.

[vercel]

@petersdt is attempting to deploy a commit to the 1nonly's projects Team on Vercel.

A member of the Team first needs to authorize it.

[1nonlypiece]

@petersdt please resolve the conflicts