fix: address validation

[jvsena42]

Fixes #354

Description

This PR implement the balance validation of #354

Preview

zero-balance-scan-zero-amount-invoice.webm

zero-balance-sance-ln-amount-invoice.webm

invalid.webm

network-mismatch.webm

insufficient-savingsbalance-uniffied.webm

QA Notes

• Bitkit should auto cap max limit (Android only) #611 will be fixed on other PR
• Test cases in Address/balance validation on 'Send Bitcoin' #354
• Extra test cases:
  • 0 balance, scan zero amount invoice -> show "Insufficient Savings" toast
  • 0 spending balance, scan lightning invoice w/ amount -> show "x more needed to pay this Lightning invoice" toast

[Copilot]

Pull request overview

This PR implements balance validation for Bitcoin and Lightning invoice payments to address issue #354. The changes ensure users receive appropriate error messages when attempting to pay invoices with insufficient balance, invalid addresses, or network mismatches.

Changes:

• Added network validation logic to detect and reject addresses from incompatible Bitcoin networks (mainnet/testnet/regtest)
• Implemented balance validation for both on-chain and Lightning invoices with specific error messages showing the shortfall amount
• Added debounced address validation with immediate user feedback via toast messages

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
NetworkValidationHelper.kt	New utility class for detecting Bitcoin network from address prefixes and validating network compatibility
NetworkValidationHelperTest.kt	Comprehensive unit tests covering address network detection and mismatch validation scenarios
AppViewModel.kt	Integrated address validation with debouncing, balance checks, and user feedback for both input and scan flows
strings.xml	Added new error message string for insufficient spending balance on Lightning invoices

[jvsena42]

@piotr-iohk needs an update from E2E