Crowdfund: Fix perk value display (#3060)
Crowdfund: Fix perk value display (#3060)

Previously this didn't take into account the target currency. This leads to wrong values if the target currency is SATS and the invoice currency is BTC. This updates the value to be calculated with the rate and also takes into account the network fee. (Basically adjusting it to how the contribution values are calculated)
btcpayserver/btcpayserver,btcpayserver/btcpayserver,btcpayserver/btcpayserver,btcpayserver/btcpayserver