feat: rich item tooltips in vendor and loot-roll windows

- Vendor window: replace manual stat-only tooltip with full renderItemTooltip
  (now shows bind type, slot, weapon stats, armor, extra stats, spell effects,
  flavor text, and sell price — consistent with inventory)
- Loot-roll popup: add item icon and hover tooltip via renderItemTooltip
- Loot-roll: pre-fetch item info via queryItemInfo when roll prompt appears

src/game/game_handler.cpp

@@ -18567,6 +18567,8 @@ void GameHandler::handleLootRoll(network::Packet& packet) {
         pendingLootRoll_.objectGuid        = objectGuid;
         pendingLootRoll_.slot              = slot;
         pendingLootRoll_.itemId            = itemId;
+        // Ensure item info is in cache; query if not
+        queryItemInfo(itemId, 0);
         // Look up item name from cache
         auto* info = getItemInfo(itemId);
         pendingLootRoll_.itemName  = info ? info->name : std::to_string(itemId);