Make the now-playing bar's title/artist clickable and add a cover art lightbox

The song title links to its album, the artist name links to the artist
page, and clicking the cover art opens a larger version in a modal.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014r98AtcBbevpscWLsfwVvv

internal/web/views.go

@@ -28,6 +28,7 @@ type SongRow struct {
 	ID              string
 	Title           string
 	ArtistName      string
+	ArtistID        string
 	AlbumTitle      string
 	AlbumID         string
 	CoverArtID      string
@@ -81,6 +82,9 @@ func toSongRow(db *sql.DB, s *database.Song, album *database.Album, userID strin
 			row.ArtistName += ", " + n
 		}
 	}
+	if id, err := database.PrimarySongArtistID(db, s.ID); err == nil {
+		row.ArtistID = id
+	}
 	if album != nil {
 		row.AlbumTitle = album.Title
 		row.AlbumID = album.ID