bolt12: Zeus sends sats when user specifies fiat

[chrisguida]

Describe the bug

When paying bolt12 offers, the user has the option of specifying the amount they'd like to pay in their fiat currency of choice, or sats, or BTC.

When specifying in fiat, Zeus appears to do the conversion into sats properly, but then when the invoice is actually fetched, the invoice is denominated in sats, with the amount the user entered for fiat. So, for example, if a user is attempting to send US$10 to the bolt12 receiver, the user selects dollars as their denomination and enters "10". Zeus appears to convert this properly to 9,577 sats using the USD exchange rate:

However, when the user taps "proceed", the actual invoice fetched says 10 sats, rather than 9,577 sats, which has resulted in several hilariously small payments to my bolt12 offer:

Reproduce

Follow steps above

ZEUS version

v0.9.4

Node interface

Core Lightning (CLNRest)

Network

Clearnet

Device

Android Pixel 8a

Device operating system

Android 15

Log output