feat: add title selection window with CMSG_SET_TITLE support

Track player titles from SMSG_TITLE_EARNED into knownTitleBits_ set,
read active title from PLAYER_CHOSEN_TITLE update field (WotLK index
1349), expose via getFormattedTitle()/sendSetTitle() on GameHandler.

Add SetTitlePacket builder (CMSG_SET_TITLE: int32 titleBit, -1=clear).

Titles window (H key) lists all earned titles from CharTitles.dbc,
highlights the active one in gold, and lets the player click to equip
or unequip a title with a single server round-trip.

include/ui/game_screen.hpp

@@ -429,6 +429,10 @@ private:
     char  achievementSearchBuf_[128] = {};
     void  renderAchievementWindow(game::GameHandler& gameHandler);
 
+    // Titles window
+    bool  showTitlesWindow_ = false;
+    void  renderTitlesWindow(game::GameHandler& gameHandler);
+
     // GM Ticket window
     bool  showGmTicketWindow_ = false;
     char  gmTicketBuf_[2048] = {};