Navigate Buzz threads more clearly on mobile

Buzz on mobile now uses two levels of back navigation. Going back or swiping from a conversation returns to the Buzz thread list first, while a separate Back to Hive action exits Buzz.

Open a Buzz conversation on mobile, then use the back gesture or control to return to your thread list. Use Back to Hive when you are ready to leave Buzz.

This helps mobile Buzz users move between conversations without accidentally leaving Buzz and makes the exit path clearer.