## Why
The playing URI was being cleared every time we leave the File Page, I believe to prevent the floating from continue playing outside of the File Page.
## Approach
Close FileRenderMobile by checking playingUri/primaryURI instead.
For the case of livestreams, just display it.
- CommentsList needs to return a title with comment amounts
- mobile player dimensions needed to fill in the cover
- hid livestream header for now until figuring out a better presentation
- ~colum-reverse~ was causing problems with MUI's drawer scrolling, so reversed the chat order and made it ~column~ by default
- Hid bottom expand navigation if component not yet opened
- some other style changes in the middle
- Biggest change: Moved mobile player logic outside of fileRenderFloating into its own component fileRenderMobile, since there is no need for all that extra resizing and dragging code (for now, as mobile doesn't have a floating player)
- Moved player to the header height
- Removed rounded borders and margins
