In transaction details, display fee in fiat when wallet is viewed in fiat #137

Inside a wallet, the user can tap on the wallet value to change between displaying transaction amounts in crypto or fiat.

When you tap on a transaction and choose "Show Details", the network fee is displayed, but it's displayed in crypto no matter what view is applied.

I propose displaying the fee in accordance with the current wallet view, that is, in crypto when crypto is selected, and in fiat when fiat is selected. For the latter, do the conversion with the exchange rate at the time of sending, so the text should also change to "Network fee (when sent):".

Thanks!