make search bar on tracks page Ctrl+F focusable; reset tracklist selection on clear

ui/browsing/trackspage.go

@@ -88,6 +88,12 @@ func (t *TracksPage) OnSongChange(track *subsonic.Child, lastScrobbledIfAny *sub
 	}
 }
 
+var _ Searchable = (*TracksPage)(nil)
+
+func (t *TracksPage) SearchWidget() fyne.Focusable {
+	return t.searcher.Entry
+}
+
 func (t *TracksPage) OnSearched(query string) {
 	t.searchText = query
 	if query == "" {

ui/widgets/tracklist.go

@@ -201,6 +201,7 @@ func (t *Tracklist) IncrementPlayCount(trackID string) {
 
 // Remove all tracks from the tracklist. Thread-safe.
 func (t *Tracklist) Clear() {
+	t.selectionMgr.UnselectAll()
 	t.tracksMutex.Lock()
 	defer t.tracksMutex.Unlock()
 	t.Tracks = nil