[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/tabs/tournament_tab_game_extension.h

@@ -0,0 +1,57 @@
+#ifndef TOURNAMENT_TAB_GAME_EXTENSION_H
+#define TOURNAMENT_TAB_GAME_EXTENSION_H
+
+#include <QObject>
+#include <QPointer>
+#include <libcockatrice/protocol/pb/event_tournament_state.pb.h>
+
+class QLabel;
+class QPushButton;
+class QWidget;
+class TournamentWidget;
+class TabGame;
+
+/**
+ * @class TournamentTabGameExtension
+ * @ingroup GameViews
+ * @brief Attaches tournament behavior to a TabGame hosting a tournament hub game.
+ *
+ * Owns the tournament overview page inside the tab's stacked main widget,
+ * mirrors tournament state onto the always-visible deck-view status strip,
+ * and routes user intents (open match game, change settings, switch pages)
+ * between the two views.
+ */
+class TournamentTabGameExtension : public QObject
+{
+    Q_OBJECT
+public:
+    explicit TournamentTabGameExtension(TabGame *parent);
+
+    void initializeTournamentMode();
+    void retranslateUi();
+
+private slots:
+    void onTournamentStateChanged(const Event_TournamentState &state);
+    void showTournamentSettingsDialog();
+    void showOverviewPage();
+    void showDeckViewPage();
+    void openMatchGame(int gameId);
+
+private:
+    void connectSignals();
+    [[nodiscard]] bool isLocalPlayerHost() const;
+    void updateDeckViewStrip(const Event_TournamentState &state);
+    void updateNavigationButtons(const Event_TournamentState &state);
+
+    QPointer<TabGame> tabGame;
+    TournamentWidget *tournamentWidget = nullptr;
+    QWidget *tournamentOverviewWidget = nullptr;
+    QPushButton *backToGameButton = nullptr;
+    QPushButton *standingsButton = nullptr;
+    QPushButton *settingsButton = nullptr;
+    QLabel *deckViewStatusLabel = nullptr;
+    Event_TournamentState::TournamentPhase lastKnownPhase = Event_TournamentState::PHASE_DECK_BUILDING;
+    bool hasLastKnownPhase = false;
+};
+
+#endif // TOURNAMENT_TAB_GAME_EXTENSION_H