Add PKCS11 token support with tests and documentation

[rajanarahul93]

Add PKCS11 Token Support

Description

This PR adds support for PKCS11 tokens (HSMs) with secp256k1 curve support to HWI. The implementation allows users to use PKCS11-compliant hardware security modules as Bitcoin hardware wallets.

Changes Made

1. Added PKCS11 client implementation in hwilib/devices/pkcs11.py
2. Created comprehensive test suite in test/test_pkcs11.py
3. Updated test runner in test/run_tests.py to include PKCS11 tests
4. Added documentation in README.md
5. Added Windows-specific prerequisites and installation instructions

Features

• Support for PKCS11 tokens with secp256k1 curve
• Cross-platform support (Windows, Linux, macOS)
• Full test coverage
• Integration with existing test framework
• Documentation and usage examples

Testing

To run the tests:

python test/run_tests.py

Usage

1. Set environment variables:

# Windows
$env:PKCS11_LIB_PATH = "C:\path\to\your\pkcs11\library.dll"
$env:PKCS11_TOKEN_LABEL = "YourTokenLabel"

# Unix-like
export PKCS11_LIB_PATH=/path/to/your/pkcs11/library.so
export PKCS11_TOKEN_LABEL=YourTokenLabel

2. Use with HWI:

hwi --device-type pkcs11 --path /path/to/library.so getmasterxpub

Dependencies

• python-pkcs11>=0.7.0
• OpenSSL development libraries
• Visual Studio Build Tools (Windows)

Related Issues

Closes #774