Wallet UX fixes: rejection handling, pending pay state, network refresh, dialog close on disconnect

[Dev-makeem]

Closes #910
Closes #909
Closes #908
Closes #907

Summary

bd8fcee: Show wallet rejection as a cancellation, not an app error (#910)
Added utils/walletErrors.ts with isWalletRejection and friendlyWalletError, which map a user-declined wallet prompt to a neutral "Request cancelled in your wallet" message. pay in hooks/useInvoice.ts now passes the payInvoice result through it.

22acd66: Disable Pay Invoice button while a transaction is pending (#909)
The confirmation modal already disabled its buttons while submitting. The remaining gap was the "Pay Invoice" trigger button in InvoicePayment.tsx, which now also disables while submitting is true.

c5cbcee: Refresh wallet network on window focus after switching (#908)
subscribe in hooks/useWallet.ts now re-reads the account and network on window focus and when the tab becomes visible, so a network switch in Freighter is reflected right away instead of after the next 5 second poll. Listeners are removed on last unsubscribe.

7cfc846: Close pay confirmation dialog when the wallet disconnects (#907)
PayConfirmationModal.tsx now reads the shared wallet state and calls onCancel if the wallet becomes disconnected while the dialog is open and no payment is submitting.

[drips-wave]

@Dev-makeem Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits