[Enhancement] Improve the chat card header

[Pjb518]

We can remove the speaker and delete button from the top of chat cards and fold them into our custom header to save on space. We can also tint the header section to match the player colour, to help identify who prompted a given card.

Note: We must be careful not to remove the message-content div from the card, as Foundry uses this to hide cards which users do not have permission to view.