fix(services): use the proper NOTIFY signal for Lyrics::hasLyrics (#2046)

* fix(services): emit proper NOTIFY for lyrics hasLyrics property

hasLyrics was declared with NOTIFY lyricsChanged, but setLines() emits lyricsChanged before updating m_hasLyrics, and clearLines() emits only hasLyricsChanged(). This made QML bindings on hasLyrics read stale values: lyrics sometimes appearing not loaded, and old lyrics remaining present (invisible but clickable) after clearing. Wire the property to the dedicated hasLyricsChanged() signal, which already fires after m_hasLyrics is set in both places.

* fix(services): remove redundant lyrics QML workaround

* fix(services): avoid redundant lyrics notifications