Cannot split more than (2^32) - 1 tokens at a time

[ebrakke]

While unlikely in a normal use case with sats, the code for splitting tokens does not support more than (2**32 - 1)` at a time.
I could honestly go either way whether on not it should be supported (since someone would have to send that many sats in a single LN invoice), but at the very least it'd probably be good to throw an error if a user tried to mint more than this amount.

[dipunm]

42 BTC if measured in sats (as opposed to having millisat tokens).
42,9496,7295 sats to be exact.