Add configurable parameter to adjust row spacing on the Segment page (and more widely across Mautic)

Hello Mautic Team,

Description:
In Mautic 6, the Segment page currently shows excessive vertical spacing between rows. This causes nearly 50% of the screen space to be wasted, especially on smaller monitors or when working with larger datasets.

This makes it harder to scan through lists quickly, reduces efficiency, and requires more scrolling than necessary.

Proposed Feature:
Introduce a configuration parameter in Mautic’s global UI settings (and/or user preferences) that allows administrators or users to adjust the vertical spacing (row padding/margin) between rows on list-based pages.

* Default spacing can remain as is for consistency.
* Users should have the option to reduce or increase row spacing depending on their preference or screen size.
* This configuration should be applied not only to Segments, but ideally more widely across Mautic’s list-based UIs (e.g., Contacts, Emails, Campaigns).

Benefits:
* Improves usability and accessibility for different workflows.
* Allows users to fit more data on-screen without constantly scrolling reducing RSI.
* Makes Mautic more flexible for power users working with large datasets.

Example Implementation Ideas:
* Add a setting under *Configuration → UI Settings* (e.g., “Row density” with options: Compact / Comfortable / Default).
* Alternatively, make it a per-user preference to support different working styles.
* Implement via a simple CSS class switch (e.g., `.row-density-compact`, `.row-density-default`).

Priority / Impact:
* Enhances productivity for all users, particularly those managing large datasets daily.
* Aligns Mautic with other modern SaaS products (e.g., Gmail, Trello) that offer density/spacing preferences.

Thank you for considering this improvement and for your continued work on making Mautic more flexible and user-friendly.