Currently after #837 is fixed, the send bonuses feature only accepts a value in USD and converts it into sats at the time of confirmation + sending

Let's improve this functionality with the following requirements:

• use the project currency to provide a real-time conversion from sats to fiat
• allow the user to type in either SATS or the fiat currency configured for the project
• if the project currency is already SATS then no need to provide conversion