[Cashtab] Add max qty validation to isValidTokenSendOrBurnAmount

Summary:
Depends on D16949

This has been overlooked in Cashtab. In practice, most users would not have a balance of a token greater than this amount (since it takes multiple max-qty mint txs and token markets are not yet supported).

It is part of the spec tho, and may not be an edge case for long. Add it.

Test Plan: npm test

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D16950