Refactor: Implement type-safe Wallet factory methods and update to Kth 0.71.0

[fpelliccioni]

Summary

This PR introduces type-safe factory methods for the Wallet class and updates the Knuth C/C++ core dependency to v0.71.0.

Changes

Wallet API Refactor (Type Safety)

• ✅ Add Wallet.fromMnemonic() factory method for creating wallets from BIP39 mnemonics
• ✅ Add Wallet.fromSeed() factory method for creating wallets from raw seeds
• ✅ Make Wallet constructor private to enforce compile-time type safety
• ✅ Prevent runtime errors when passing string instead of string[] for mnemonics

Core Dependency Update

• ✅ Update Knuth C/C++ core from v0.70.0 to v0.71.0
• ✅ Recompiled WASM binaries with latest core

Test Improvements

• ✅ Update all tests to use new factory methods
• ✅ Fix hardcoded build timestamps that would fail on user builds
• ✅ Update version expectations to 0.71.0

Package Version

• ✅ Bump version from 2.7.0 to 2.8.0

Migration Guide

Before:

const wallet = new Wallet(mnemonic, derivationPath, network);

After:

// For mnemonics (recommended)
const wallet = Wallet.fromMnemonic(mnemonic, derivationPath, network);

// For raw seeds (advanced usage)
const wallet = Wallet.fromSeed(seed, derivationPath, network);

Breaking Changes

⚠️ The Wallet constructor is now private. Use the factory methods instead.

Test Plan

• All existing tests pass with new API
• Type safety verified at compile time
• Build timestamps no longer hardcoded