[Client] Add tournament UI for creating and following lobby tournaments

Wires the tournament protocol into the client:
- DlgCreateGame gains a tournament checkbox with a games-per-match
  settings sub-dialog; both values are sent with Command_CreateGame and
  mirrored in the join-info variant of the dialog
- TournamentWidget renders live standings (with deck-submission state)
  and pairings for the local player's perspective, and asks to open the
  current match game via openMatchGameRequested()
- TournamentTabGameExtension attaches an overview page to TabGame's
  stacked views, mirrors phase and submission progress onto a deck-view
  status strip, and provides round-trip navigation between game view and
  standings; hosts get an in-game settings dialog during deck building
- Open-match falls back to joining as spectator through TabSupervisor;
  sub-games now return to their parent tab on close, falling back to
  the normal leave-game flow when the parent is gone

cockatrice/src/interface/widgets/dialogs/dlg_tournament_settings.h

@@ -0,0 +1,30 @@
+#ifndef DLG_TOURNAMENT_SETTINGS_H
+#define DLG_TOURNAMENT_SETTINGS_H
+
+#include <QDialog>
+
+class QDialogButtonBox;
+class QSpinBox;
+
+struct DlgTournamentSettingsResult
+{
+    int gamesPerMatch = 1;
+};
+
+class DlgTournamentSettings : public QDialog
+{
+    Q_OBJECT
+public:
+    explicit DlgTournamentSettings(QWidget *parent = nullptr);
+    DlgTournamentSettingsResult getResult() const;
+    void setCurrentGamesPerMatch(int n);
+
+private slots:
+    void actOK();
+
+private:
+    QSpinBox *gamesPerMatchSpin;
+    QDialogButtonBox *buttonBox;
+};
+
+#endif