Fix withdrawal amount handling on frontend

[Jossec101]

Ensure the withdrawal amount is set correctly when saving

[Copilot]

Pull Request Overview

This PR ensures that withdrawal destinations and their amounts are correctly initialized on the frontend and that each destination record has proper timestamps in the repository layer.

• Frontend: Initialize WalletWithdrawalRequestDestinations with the correct amount when saving and handle edits to the destination address.
• Frontend: Reset destination list on address change (currently to zero, but this may need adjustment).
• Backend: Set creation and update datetimes for each withdrawal destination.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Pages/Withdrawals.razor	Adds and updates initialization of WalletWithdrawalRequestDestinations on save and address edit.
src/Data/Repositories/WalletWithdrawalRequestRepository.cs	Initializes creation/update datetimes for each destination.

Comments suppressed due to low confidence (2)

src/Data/Repositories/WalletWithdrawalRequestRepository.cs:138

• [nitpick] The comment refers to "types" but the code is setting creation/update timestamps. Consider updating it to "// Set creation and update datetimes for each destination".

            // Set the types for the destinations

src/Pages/Withdrawals.razor:593

• The variable amount is not defined in this context, which will cause a compilation error. Consider using _amount or the calculated value from _selectedUTXOs.

                Amount = amount