* save fiat_amounts on payment creation
* show fiat amount in frontend
* add lnbits_default_accounting_currency
* extract fiat calculation logic into service
* move all currency conversions to calc_fiat_amounts
move all conversion logic into create_invoice so extensions can benefit aswell
* show user-defined and wallet-defined currency in frontend
* remove sat from fiat units
* make bundle
* improve tests
* debug log