feat: Sparkline for batch exports

[tiina303]

Problem

Fixed the typing around the PipelineNodeMetrics too which worked, because types aren't enforced.

Changes

👉 Stay up-to-date with PostHog coding conventions for a smoother review.

Does this work well for both Cloud and self-hosted?

How did you test this code?

Localhost saw a sparkline for weekly volume for a batch export

[github-actions[bot]]

Size Change: 0 B

Total Size: 1.05 MB

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Filename	Size
frontend/dist/toolbar.js	1.05 MB

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