feat: resolve item icon paths from ItemDisplayInfo.dbc for Lua API

Add ItemIconPathResolver that lazily loads ItemDisplayInfo.dbc to map
displayInfoId → icon texture path. This fixes three Lua API functions
that previously returned nil for item icons:

- GetItemInfo() field 10 (texture) now returns the icon path
- GetActionTexture() for item-type action bar slots now returns icons
- GetLootSlotInfo() field 1 (texture) now returns proper item icons
  instead of incorrectly using the spell icon resolver

Follows the same lazy-loading pattern as SpellIconPathResolver. The DBC
is loaded once on first query and cached for all subsequent lookups.

include/game/game_handler.hpp

@@ -294,6 +294,13 @@ public:
         return spellIconPathResolver_ ? spellIconPathResolver_(spellId) : std::string{};
     }
 
+    // Item icon path resolver: displayInfoId -> texture path (e.g., "Interface\\Icons\\INV_Sword_04")
+    using ItemIconPathResolver = std::function<std::string(uint32_t)>;
+    void setItemIconPathResolver(ItemIconPathResolver r) { itemIconPathResolver_ = std::move(r); }
+    std::string getItemIconPath(uint32_t displayInfoId) const {
+        return itemIconPathResolver_ ? itemIconPathResolver_(displayInfoId) : std::string{};
+    }
+
     // Random property/suffix name resolver: randomPropertyId -> suffix name (e.g., "of the Eagle")
     // Positive IDs → ItemRandomProperties.dbc; negative IDs → ItemRandomSuffix.dbc (abs value)
     using RandomPropertyNameResolver = std::function<std::string(int32_t)>;
@@ -2662,6 +2669,7 @@ private:
     AddonChatCallback addonChatCallback_;
     AddonEventCallback addonEventCallback_;
     SpellIconPathResolver spellIconPathResolver_;
+    ItemIconPathResolver itemIconPathResolver_;
     RandomPropertyNameResolver randomPropertyNameResolver_;
     EmoteAnimCallback emoteAnimCallback_;