Improve error message for melting small tokens

[gudnuf]

Most mints have a minimum lightning fee reserve of 2 sats. This means that its usually impossible to melt 2 or 1 sats.

I have the following error messages (hooks/cashu/useCashu) to handle this case, but they do not consider receiving small tokens. The error messages are specific to transferring between accounts.

The error should know if the cross mint swap is happening in the context of claiming a token or transferring between mints in the Accounts tab