Support Max staking amount

[jrwbabylonlab]

In the Figma design, we aim to support a feature where users can click “Max” to stake the maximum amount possible.

The main challenge to address is the chicken-and-egg problem between the max staking amount and the fee. Specifically, the max staking amount + fee should equal the user’s total stakable balance. However, the fee is determined based on the staking amount, as it affects how many UTXOs are used, which in turn impacts the fee calculation.