[Chat] Render game link buttons (#7135)

* [Chat] Render cockatrice://joingame links in chat as clickable buttons

Words starting with cockatrice:// become button-style anchors labelled with
the game description, id and server (falling back to id + server for links
built without a description). The description is spliced via the multi-arg
arg() overloads so a title containing "%…" cannot corrupt the label.

Keyboard link access is enabled so the anchors are reachable without a mouse.

* [Chat] Fix percent-encoding and scheme gating in game-link chat labels

Game descriptions containing '%' were rendered as '%25' in the chat
button label because QUrlQuery's default decode leaves %25 untouched.
Use QUrl::FullyDecoded for the description item, and restrict the
invite-button treatment to cockatrice://joingame links; any other
cockatrice:// scheme now falls through to plain text.

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Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

cockatrice/src/interface/widgets/server/chat_view/chat_view.h

@@ -71,6 +71,7 @@ private:
     void scrollToBottom();
     void appendCardTag(QTextCursor &cursor, const QString &cardName);
     void appendUrlTag(QTextCursor &cursor, QString url);
+    void appendGameLinkTag(QTextCursor &cursor, const QString &url);
     static QColor getCustomMentionColor();
     static QColor getCustomHighlightColor();
     void showSystemPopup(const QString &userName);