feat: artist/page endpoint, multi-disc fix, playlist ownership, UX improvements

- Switch artist view to artist/page API (proper sections: Albums, Singles & EPs,
  Live, Compilations; version in titles like "Deluxe")
- Fix artist sections categorization using releases[].type from artist/page
- Add getUser() backend call; fetch on session restore when userId=0 to fix
  playlist ownership (Remove from playlist / Delete playlist were missing)
- Fix multi-disc double-click / Play Now queue start index (disc headers were
  counted in row index but excluded from currentTracksJson)
- Hide redundant Album column when viewing an album
- Make artist name in context header clickable (navigates to artist page)
- Fix gap between title and artist name in context header (addStretch)
- Fix queue panel track titles to include version field
- Fix album list to show version in title column

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/backend/qobuzbackend.cpp

@@ -35,6 +35,11 @@ void QobuzBackend::setToken(const QString &token)
     qobuz_backend_set_token(m_backend, token.toUtf8().constData());
 }
 
+void QobuzBackend::getUser()
+{
+    qobuz_backend_get_user(m_backend);
+}
+
 // ---- catalog ----
 
 void QobuzBackend::search(const QString &query, quint32 offset, quint32 limit)
@@ -249,6 +254,9 @@ void QobuzBackend::onEvent(int eventType, const QString &json)
     case 22: // EV_PLAYLIST_TRACK_ADDED
         emit playlistTrackAdded(static_cast<qint64>(obj["playlist_id"].toDouble()));
         break;
+    case EV_USER_OK:
+        emit userLoaded(obj);
+        break;
     case EV_GENERIC_ERR:
     case EV_TRACK_URL_ERR:
         emit error(obj["error"].toString());