MediaSession pause requests may happen even when Funkwhale is already in a
paused state. Previously FW would flip between play/pause without
consideration for the current state instead of doing nothing when
the playback state matches the requested one.

Notably, this made Funkwhale resume audio playback when entering sleep mode
on my system.

Fixes the UI not updating when clicking the position slider while playback is paused.

Fixes #1266

The MediaSession metadata was only set on track change, but not for the track already set during load.

Fixes #1252

Minor UI enhancements to player queue (more visible progress on bottom player, easier to click buttons)

Set up player config for mobile control