[Feature] Add a Download All Songs button

**Packages**

Media

**Describe the solution you'd like**

Rather than having to download all songs one by one, have a button that downloads them all.

Probably makes sense to put this on the Songs page.

**Describe alternatives you've considered**

Download them individually

**Additional context**

N/A

Start by locating the Songs page and the existing individual-song download entry point. The work is done when that page provides a Download All Songs button that downloads every song, while individual downloads continue to work.

Written by the indexing model from the issue text.