fix: issue with fee UI react rendering loop

[jrwbabylonlab]

The bug happens when you stake amount + fee > funds avaiable:

1. "Loading transaction fee amount..." forever
2. Keep showing popup like below (periodically which interrupted the user interaction with dApp)

3. preview modal was shown when staking form data isn't valid. in this case, the fee is 0. and 4. No clear message about funds not enough to cover fees

This is a high-risk change, but it’s the least invasive approach I could think of without breaking other functionality.

What’s wrong with the current implementation?

The three components are currently tangled together:

•	staking.tsx
•	stakingAmount.tsx
•	stakingFee.tsx

The stakingFeeSat is derived in staking.tsx, but it’s passed as a prop to stakingFee.tsx and is affected by selectedFeeRate, which is also set within stakingFee.tsx. This results in two different places determining the fee values.

To make it more complex, stakingAmount.tsx handles input validation and decides the value that will determine UTXOs, which in turn affects the fees. As a result, these three components create a very complex interdependent React data flow through props and state.

I didn’t attempt to fix these interdependencies in this PR because doing so would require much larger changes. The ideal state I envision is:

•	All fee logic should reside only within stakingFee.tsx.
•	stakingFee.tsx should be a child component of stakingAmount.tsx.
•	The Preview modal component should obtain the value directly from stakingAmount.tsx using hooks. We don’t need onStakingAmountSatChange; instead, we need a getValidStakingAmount function when rendering the preview modal.

As a result of this PR, you’ll notice that the StakingFee component re-renders with each amount input. This isn’t avoidable unless we untangle the three components mentioned above. While it’s not ideal, it’s something we can live with for now until we refactor.

[vitsalis]

Why are we doing this instead of what we had before? Seems that we have a different behavior for mempool fee rates

[jrwbabylonlab]

Going to close this PR as it introduce too much risk for the up coming release.