feat: BIP48 shared (multisignature) accounts

[sneurlax]

• Adapt FROST creation/resharing screens/UI for MultisigCoordinator (or the musig/BIP48 process in general).
• Finish BIP48Wallet
  • new/next address derivation
    see https://github.com/cypherstack/bip48/blob/main/example/bip48_example.dart
  • partially signed transaction caching
• Finish tap/NFC functionality integration.
  • "Tap to read cosigner key"
  • "Tap to share cosigner key"
  • Add iOS entitlements etc. ... see https://github.com/okadan/flutter-nfc-manager?tab=readme-ov-file#setup (optional)
• Make backup/recovery view showing MultisigParams info that must be saved
  • Add this to Stack Wallet Backups or similar (optional)
• Create new wallet from the results of the MultisigSetupView/BIP48 process.
• Add fallback data-exchange methods:
  • Copy and paste xpubs etc
  • QR Code scanning
• Update the multisig_coordinator package with anything new from the final MultisigCoordinator and/or MultisigParams, then publish and use it.

This button needs to be pushed down:

[sneurlax]

Closed pending completion.

[sneurlax]

I'd like to add vectors for all script types at least as per Trezor shared accounts. Would also like to add Ledger and Copay vectors if possible