Improve interaction with the slider widget #12784

[rowheat02]

Description

This PR extends the click of the slider for selection. Now the user can also select anywhere on the slider, not on a tick label or marker. The nearest one will be selected.

Screen.Recording.2026-08-17.at.19.29.08.mov

Also, it fixes color consistency on ticks for the slider. So now it looks black like in the chart.

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/geosolutions-it/MapStore2/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x", remove the others)

• Enhancement

Issue

What is the current behavior?

#12784
#12782

What is the new behavior?

• Now it is easier to select item from slider.
• Tick color same as charts.

Breaking change

Does this PR introduce a breaking change? (check one with "x", remove the other)

• Yes, and I documented them in migration notes
• No

Other useful information