Add bag bar drag-to-reorder, fix three wrong WotLK opcodes

Bag bar: left-click drag bags to swap positions using CMSG_SWAP_ITEM
with INVENTORY_SLOT_BAG_0 (255). Local optimistic swap for instant
feedback. Camera controller now respects ImGui WantCaptureMouse.
Vendor auto-open bags only triggers once per session.

Fix opcodes: CMSG_GAMEOBJECT_USE 0x01B→0x0B1 (typo caused
SMSG_FORCEACTIONSHOW spam), CMSG_CANCEL_AURA 0x033→0x136,
SMSG_SELL_ITEM 0x1A4→0x1A1.

include/game/inventory.hpp

@@ -95,6 +95,9 @@ public:
     uint8_t getPurchasedBankBagSlots() const { return purchasedBankBagSlots_; }
     void setPurchasedBankBagSlots(uint8_t count) { purchasedBankBagSlots_ = count; }
 
+    // Swap two bag slots (equip items + contents)
+    void swapBagContents(int bagA, int bagB);
+
     // Utility
     int findFreeBackpackSlot() const;
     bool addItem(const ItemDef& item);