[UX Improvement] Adjust Vertical Spacing for Clearer Date Grouping in Timeline

[RtYkk]

Clear and concise description of the problem

The current uniform vertical spacing around date headers causes them to feel disconnected from their content. This weakens the visual grouping of the timeline and reduces scannability.

Suggested solution

A "tight-then-loose" spacing strategy would improve the visual hierarchy:

1. Reduce the space between a date header and the first item below it. This visually anchors the header to its content.
2. Increase the space after the last item in a group and before the next date header. This creates a clear separation between groups.

Alternative

No response

Additional context

Validations

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[linear]

FOL-2653