Add chat input history navigation with Up/Down arrows

Up arrow in the chat input field recalls previously sent messages.
Down arrow moves forward through history; going past the end clears input.
History stores up to 50 unique entries and resets position after each send.

include/ui/game_screen.hpp

@@ -50,6 +50,10 @@ private:
     int lastChatType = 0;  // Track chat type changes
     bool chatInputMoveCursorToEnd = false;
 
+    // Chat sent-message history (Up/Down arrow recall)
+    std::vector<std::string> chatSentHistory_;
+    int chatHistoryIdx_ = -1;  // -1 = not browsing history
+
     // Chat tabs
     int activeChatTab_ = 0;
     struct ChatTab {