Cashu backend: Parsing Error and UX Issue During Payment

We encountered a parsing error in the logs when attempting to process a numeric value. The error message is as follows:

`strconv.ParseInt: parsing "10.000": invalid syntax`

This indicates a potential issue with number formatting,

Additionally, a UX error is displayed during payment attempts:

`Failed to send payment. Error: 500 Proofs are pending`

Error logs of this issue are on our private [slack](https://getalby.slack.com/archives/C02T4A5BZJS/p1732804562229809)