Add some Callbacks for trade release

Through this, I request that the developers add the following global callbacks to the LuaAPI so that we can create custom scripts that allow us to perform trades with other currencies. Currently, I am trying to perform this action with `onUseCommand`, but the way I am doing it is not very effective since I am basing everything on caching.

In practice, these callbacks fulfill 3 different roles in the trade flow:

Handshake / Lock the offer (anti-snipe / anti-swap with another)

`onTradeRequest(seller, buyer)` and/or `onTradeAccept(seller, buyer)`

Here we identify who the seller is (who opened the shop), inform the price/currency to the buyer, and lock that offer for that buyer for a few seconds.

Finalization (exact moment to charge)

onTradeConfirm(seller, buyer) and/or onTradeOk(seller, buyer)

• This allows us to:
• validate the buyer's balance,
• debit the buyer,
• credit the seller,
• and block the trade if there is insufficient balance (returning 1).

Cancellation / Clearing

onTradeCancel(seller, buyer)
Releases locks, cancels the session, and avoids state garbage.