Add mail item attachment support for sending

- CMSG_SEND_MAIL now includes item GUIDs (up to 12 per WotLK)
- Right-click items in bags to attach when mail compose is open
- Compose window shows 12-slot attachment grid with item icons
- Click attached items to remove them
- Classic/Vanilla falls back to single item GUID format

src/game/game_handler.cpp

@@ -12851,10 +12851,114 @@ void GameHandler::sendMail(const std::string& recipient, const std::string& subj
         LOG_WARNING("sendMail: mailboxGuid_ is 0 (mailbox closed?)");
         return;
     }
-    auto packet = packetParsers_->buildSendMail(mailboxGuid_, recipient, subject, body, money, cod);
+    // Collect attached item GUIDs
+    std::vector<uint64_t> itemGuids;
+    for (const auto& att : mailAttachments_) {
+        if (att.occupied()) {
+            itemGuids.push_back(att.itemGuid);
+        }
+    }
+    auto packet = packetParsers_->buildSendMail(mailboxGuid_, recipient, subject, body, money, cod, itemGuids);
     LOG_INFO("sendMail: to='", recipient, "' subject='", subject, "' money=", money,
-             " mailboxGuid=", mailboxGuid_);
+             " attachments=", itemGuids.size(), " mailboxGuid=", mailboxGuid_);
     socket->send(packet);
+    clearMailAttachments();
+}
+
+bool GameHandler::attachItemFromBackpack(int backpackIndex) {
+    if (backpackIndex < 0 || backpackIndex >= inventory.getBackpackSize()) return false;
+    const auto& slot = inventory.getBackpackSlot(backpackIndex);
+    if (slot.empty()) return false;
+
+    uint64_t itemGuid = backpackSlotGuids_[backpackIndex];
+    if (itemGuid == 0) {
+        itemGuid = resolveOnlineItemGuid(slot.item.itemId);
+    }
+    if (itemGuid == 0) {
+        addSystemChatMessage("Cannot attach: item not found.");
+        return false;
+    }
+
+    // Check not already attached
+    for (const auto& att : mailAttachments_) {
+        if (att.occupied() && att.itemGuid == itemGuid) return false;
+    }
+
+    // Find free attachment slot
+    for (int i = 0; i < MAIL_MAX_ATTACHMENTS; ++i) {
+        if (!mailAttachments_[i].occupied()) {
+            mailAttachments_[i].itemGuid = itemGuid;
+            mailAttachments_[i].item = slot.item;
+            mailAttachments_[i].srcBag = 0xFF;
+            mailAttachments_[i].srcSlot = static_cast<uint8_t>(23 + backpackIndex);
+            LOG_INFO("Mail attach: slot=", i, " item='", slot.item.name, "' guid=0x",
+                     std::hex, itemGuid, std::dec, " from backpack[", backpackIndex, "]");
+            return true;
+        }
+    }
+    addSystemChatMessage("Cannot attach: all attachment slots full.");
+    return false;
+}
+
+bool GameHandler::attachItemFromBag(int bagIndex, int slotIndex) {
+    if (bagIndex < 0 || bagIndex >= inventory.NUM_BAG_SLOTS) return false;
+    if (slotIndex < 0 || slotIndex >= inventory.getBagSize(bagIndex)) return false;
+    const auto& slot = inventory.getBagSlot(bagIndex, slotIndex);
+    if (slot.empty()) return false;
+
+    uint64_t itemGuid = 0;
+    uint64_t bagGuid = equipSlotGuids_[19 + bagIndex];
+    if (bagGuid != 0) {
+        auto it = containerContents_.find(bagGuid);
+        if (it != containerContents_.end() && slotIndex < static_cast<int>(it->second.numSlots)) {
+            itemGuid = it->second.slotGuids[slotIndex];
+        }
+    }
+    if (itemGuid == 0) {
+        itemGuid = resolveOnlineItemGuid(slot.item.itemId);
+    }
+    if (itemGuid == 0) {
+        addSystemChatMessage("Cannot attach: item not found.");
+        return false;
+    }
+
+    for (const auto& att : mailAttachments_) {
+        if (att.occupied() && att.itemGuid == itemGuid) return false;
+    }
+
+    for (int i = 0; i < MAIL_MAX_ATTACHMENTS; ++i) {
+        if (!mailAttachments_[i].occupied()) {
+            mailAttachments_[i].itemGuid = itemGuid;
+            mailAttachments_[i].item = slot.item;
+            mailAttachments_[i].srcBag = static_cast<uint8_t>(19 + bagIndex);
+            mailAttachments_[i].srcSlot = static_cast<uint8_t>(slotIndex);
+            LOG_INFO("Mail attach: slot=", i, " item='", slot.item.name, "' guid=0x",
+                     std::hex, itemGuid, std::dec, " from bag[", bagIndex, "][", slotIndex, "]");
+            return true;
+        }
+    }
+    addSystemChatMessage("Cannot attach: all attachment slots full.");
+    return false;
+}
+
+bool GameHandler::detachMailAttachment(int attachIndex) {
+    if (attachIndex < 0 || attachIndex >= MAIL_MAX_ATTACHMENTS) return false;
+    if (!mailAttachments_[attachIndex].occupied()) return false;
+    LOG_INFO("Mail detach: slot=", attachIndex, " item='", mailAttachments_[attachIndex].item.name, "'");
+    mailAttachments_[attachIndex] = MailAttachSlot{};
+    return true;
+}
+
+void GameHandler::clearMailAttachments() {
+    for (auto& att : mailAttachments_) att = MailAttachSlot{};
+}
+
+int GameHandler::getMailAttachmentCount() const {
+    int count = 0;
+    for (const auto& att : mailAttachments_) {
+        if (att.occupied()) ++count;
+    }
+    return count;
 }
 
 void GameHandler::mailTakeMoney(uint32_t mailId) {