feat: add reputation bar above XP bar

Show a color-coded reputation progress bar for the most recently gained
faction above the XP bar. The bar is auto-shown when any faction rep
changes (watchedFactionId_ tracks the last changed faction). Colors
follow WoW conventions: red=Hated/Hostile, orange=Unfriendly,
yellow=Neutral, green=Friendly, blue=Honored, purple=Revered,
gold=Exalted. Tooltip shows exact standing values on hover.

src/game/game_handler.cpp

@@ -3546,6 +3546,7 @@ void GameHandler::handlePacket(network::Packet& packet) {
                                   delta > 0 ? "increased" : "decreased",
                                   std::abs(delta));
                     addSystemChatMessage(buf);
+                    watchedFactionId_ = factionId;
                     if (repChangeCallback_) repChangeCallback_(name, delta, standing);
                 }
                 LOG_DEBUG("SMSG_SET_FACTION_STANDING: faction=", factionId, " standing=", standing);