fix(ui): prevent duplicate getCoverArt requests on artist page

useMediaQuery defaults to false on the first render (SSR compat),
causing MobileArtistDetails to briefly render on desktop. Its CSS
background-image triggered a full-size image fetch before the
component switched to DesktopArtistDetails, which fetched again.

Pass noSsr: true so the media query evaluates synchronously, and
cap the mobile background image to 800px.

ui/src/artist/MobileArtistDetails.jsx

@@ -83,7 +83,7 @@ const useStyles = makeStyles(
 )
 
 const MobileArtistDetails = ({ artistInfo, biography, record }) => {
-  const img = subsonic.getCoverArtUrl(record)
+  const img = subsonic.getCoverArtUrl(record, 800)
   const [expanded, setExpanded] = useState(false)
   const classes = useStyles({ img, expanded })
   const title = record.name