Add setting to show/hide date separators in call history

[chrbratt]

Checklist

• I made sure that there are no existing issues - open or closed - to which I could contribute my information.
• I made sure that there are no existing discussions - open or closed - to which I could contribute my information.
• I have read the FAQs inside the app (Menu -> About -> FAQs) and my problem isn't listed.
• I have taken the time to fill in all the required details. I understand that the request will be dismissed otherwise.
• This issue contains only one feature request.
• I have read and understood the contribution guidelines.

Feature description

Add a setting to show or hide date separators/dividers in the call history.

Why do you want this feature?

Some users prefer a more compact call history list without the date dividers taking up vertical space. This is especially useful when combined with call consolidation, where the chronological grouping by date becomes less relevant.

Additional information

The setting would be a simple toggle under Settings → Calls, similar to the existing "Group subsequent calls" setting.

I have implemented this in my fork:
Adds a new switch in Settings under "Calls" to let users show or hide the date separators in the call history.
This gives users the option for a more compact list. The Recents tab now checks this setting before displaying the date dividers.