Shorten message relative date format

[ChristophWurst]

Is your feature request related to a problem? Please describe.

The relative date of a message takes up precious space of the sender name.

Describe the solution you'd like

Ref https://github.com/nextcloud/nextcloud-vue/issues/2089

• Dropping relative dates in that list for now to save space
• today: 7:24, 20:15 → H:mm
• last 6 days: Mo, Tu, We, … → dd
• same year: Aug 6, Jul 10, … → MMM D
• before that: Apr 11, 2021 → MMM D, YYYY

Describe alternatives you've considered

No response

Additional context

No response