Feature Parity with 0.x

This PR implements the remaining Node.js crypto APIs needed for feature parity with the 0.x branch, completing our 1.0.0 release goals.

New Features

generateKeyPairSync() for RSA and EC

• Previously threw "not implemented" error for RSA/RSA-PSS/EC key types
• Now fully functional using existing C++ sync implementations
• Ed25519/Ed448/X25519/X448 already worked; RSA and EC now complete the set

PKCS1 v1.5 Padding Support

• publicEncrypt/publicDecrypt now accept a padding option
• Supports both RSA_PKCS1_PADDING and RSA_PKCS1_OAEP_PADDING
• Previously only OAEP was available

privateEncrypt() and privateDecrypt()

• New functions for RSA signing-style encryption (encrypt with private key, decrypt with public key)
• Uses EVP_PKEY_sign/EVP_PKEY_verify_recover OpenSSL APIs
• Supports PKCS1 padding mode

Tests

• 10 new tests for generateKeyPairSync (RSA 2048/4096, RSA-PSS, EC P-256/P-384/P-521)
• 5 new tests for PKCS1 padding in publicEncrypt/publicDecrypt
• 11 new tests for privateEncrypt/privateDecrypt

Documentation

• Updated implementation-coverage.md to reflect new implementations
• Added clang-format rule to `.claude/rules/code-cpp.xml