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.hpp

@@ -23,6 +23,7 @@ public:
     // --- auth ---
     void login(const QString &email, const QString &password);
     void setToken(const QString &token);
+    void getUser();
 
     // --- catalog ---
     void search(const QString &query, quint32 offset = 0, quint32 limit = 20);
@@ -71,6 +72,7 @@ signals:
     // auth
     void loginSuccess(const QString &token, const QJsonObject &user);
     void loginError(const QString &error);
+    void userLoaded(const QJsonObject &user);
 
     // catalog
     void searchResult(const QJsonObject &result);