fix(ui): Align time series line graph with actual data points

[bryanhuhta]

Before this change the time series data points would render evenly across the time series graph window, regardless of whether the data point aligned with the x-axis time value.

This PR makes sure that data points are rendered above the correct time marker tick on the x-axis.

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Note

Medium Risk
Changes the timeline API contract from number[] to timestamped Point[], which touches query state and chart rendering and could break downstream consumers if any were missed. Adds a new test runner and CI job, which is low functional risk but may affect pipeline stability/time.

Overview
Fixes the time series chart so points are positioned on the x-axis using their actual timestamp instead of being evenly distributed across the width, updating the area/line paths accordingly.

Updates fetchTimeline/usePyroscopeQuery/TimeSeries to pass full { value, timestamp } points through the UI rather than mapping to just values.

Introduces vitest with a new yarn test script, moves time-series helper functions into components/timeseries.ts with unit tests, and adds a test job to the frontend GitHub Actions workflow.

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[aleks-p]

LGTM