feat: fire CHAT_MSG_* events to Lua addons for all chat types

Wire chat messages to the addon event system via AddonChatCallback.
Every chat message now fires the corresponding WoW event:

- CHAT_MSG_SAY, CHAT_MSG_YELL, CHAT_MSG_WHISPER
- CHAT_MSG_PARTY, CHAT_MSG_GUILD, CHAT_MSG_OFFICER
- CHAT_MSG_RAID, CHAT_MSG_RAID_WARNING, CHAT_MSG_BATTLEGROUND
- CHAT_MSG_SYSTEM, CHAT_MSG_CHANNEL, CHAT_MSG_EMOTE

Event handlers receive (eventName, message, senderName) arguments.
Addons can now filter, react to, or log chat messages in real-time.

include/game/game_handler.hpp

@@ -279,6 +279,10 @@ public:
     using ChatBubbleCallback = std::function<void(uint64_t, const std::string&, bool)>;
     void setChatBubbleCallback(ChatBubbleCallback cb) { chatBubbleCallback_ = std::move(cb); }
 
+    // Addon chat event callback: fires when any chat message is received (for Lua event dispatch)
+    using AddonChatCallback = std::function<void(const MessageChatData&)>;
+    void setAddonChatCallback(AddonChatCallback cb) { addonChatCallback_ = std::move(cb); }
+
     // Emote animation callback: (entityGuid, animationId)
     using EmoteAnimCallback = std::function<void(uint64_t, uint32_t)>;
     void setEmoteAnimCallback(EmoteAnimCallback cb) { emoteAnimCallback_ = std::move(cb); }
@@ -2634,6 +2638,7 @@ private:
     size_t maxChatHistory = 100;             // Maximum chat messages to keep
     std::vector<std::string> joinedChannels_;   // Active channel memberships
     ChatBubbleCallback chatBubbleCallback_;
+    AddonChatCallback addonChatCallback_;
     EmoteAnimCallback emoteAnimCallback_;
 
     // Targeting