Feature: Add button to clear chart

[SJ7F]

Summary

This adds a button which clears the chart when it is pressed

Motivation & Context

Closes #20

Changes

• Adds a trash can button to PlotToolsOverlay
• Resets the store when the button is pressed

Screenshots / Demos (if UI)

Before:

After:

How to Test

1. Connect something to start logging data
2. Click the red trash can button
3. Observe that the chart is cleared

Checklist

• I ran npm run lint and fixed any issues
• I ran npm run typecheck (TypeScript) with no errors
• I ran npm test and tests pass
• I ran npm run test:coverage if code paths changed significantly
• I added/updated tests where appropriate
• I updated docs/README if needed
• No breaking changes without clear migration notes