feat(earn): add history chart hover details

[petar-omni]

Summary

• show the nearest recorded chart value and localized date on hover
• highlight the active chart point with a dot and cursor guide
• use theme-derived contrast for the tooltip container
• add DOM and Chromium coverage for tooltip behavior

---

Note

Low Risk
UI-only chart tooltip and styling with guarded tooltip rendering; no auth, data, or API changes.

Overview
Adds hover details to earn history charts so users see the nearest point’s formatted value and a localized date while moving over the series.

HistoryChart now wires Recharts Tooltip with a new ChartTooltip, uses i18n for date formatting, optional valueFormatter (falls back to axis tickFormatter), a dashed cursor, and an active dot matching the endpoint highlight. HistoryChartSection forwards the optional formatter. Theme-based tooltip styles were added in styles.css.ts.

Tests cover empty/chart render, tooltip edge cases (inactive payload, locale, invalid values), and browser hover showing tooltip + active dot.

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Latest commit: c0b9cc6

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[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

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^{Reviewed by Cursor Bugbot for commit 7c05eae. Configure here.}

[cursor]

Hover date shifts by timezone

Medium Severity

DateTime.formatLocal converts each history timestamp into the viewer's local timezone. Chart points are UTC midnight daily snapshots, so users west of UTC see the previous calendar day on hover instead of the recorded date. Locale still applies if the UTC calendar day is formatted instead.

 

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[petar-omni]

Fixed in c0b9cc6. Snapshot dates now use DateTime.formatUtc, with a regression test forced to America/Los_Angeles that previously rendered the prior calendar day.

[cursor]

Stale comment

Risk: medium. Not approved: Cursor Bugbot finished as skipped after reporting an unresolved hover-date finding, and this user-facing earn-chart change is above the low-risk approval threshold. Human reviewers were assigned.

  

_{Sent by Cursor Approval Agent: Pull Request Router and Approver}

[cursor]

Risk: medium. Not approved: Cursor Security Agent passed with no security findings, but this user-facing earn-chart hover change is above the low-risk approval threshold. Human review is needed; reviewers were already assigned.

  

_{Sent by Cursor Approval Agent: Pull Request Router and Approver}

[raiseerco]

lgtm