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/view/maincontent.cpp

@@ -36,6 +36,11 @@ MainContent::MainContent(QobuzBackend *backend, PlayQueue *queue, QWidget *paren
                      [this] { m_tracks->playAll(false); });
     QObject::connect(m_header->shuffleButton(), &QPushButton::clicked,
                      [this] { m_tracks->playAll(true); });
+    QObject::connect(m_header->subtitleButton(), &QPushButton::clicked,
+                     [this] {
+        const qint64 id = m_header->artistId();
+        if (id > 0) emit artistRequested(id);
+    });
 
     m_albumList  = new AlbumListView(this);
     m_artistList = new ArtistListView(this);