feat: Add wallet management tools for RustChain MCP Server

[HuiNeng6]

Summary

This PR implements wallet management tools for the RustChain MCP Server as part of Bounty #2302 (75 RTC).

New Features

rustchain_crypto.py module:

• Ed25519 key pair generation and signing
• BIP39 mnemonic generation (12/24 words) and validation
• Key derivation from mnemonic seed
• AES-256-GCM encrypted keystore storage
• PBKDF2 key derivation (100,000 iterations)

9 New Wallet Tools:

1. \wallet_create\ - Generate new Ed25519 wallet with BIP39 mnemonic
2. \wallet_balance\ - Check RTC balance for any wallet ID or address
3. \wallet_history\ - Get transaction history for a wallet
4. \wallet_transfer_signed\ - Sign and submit RTC transfer from local wallet
5. \wallet_list\ - List all wallets in local keystore
6. \wallet_export\ - Export encrypted keystore JSON for backup
7. \wallet_import\ - Import wallet from keystore JSON or mnemonic
8. \wallet_export_mnemonic\ - Export BIP39 seed phrase (use with caution!)
9. \wallet_delete\ - Delete wallet from local keystore

Security Features

• Private keys encrypted at rest with AES-256-GCM
• Mnemonic stored encrypted, never exposed in tool responses
• Password-based encryption with PBKDF2 (100,000 iterations)
• Secure keystore location: ~/.rustchain/mcp_wallets/\
• Minimum 8-character password requirement

Testing

• 24 comprehensive unit tests added
• All tests passing
• Coverage includes: key generation, signing, encryption, wallet CRUD, import/export

Dependencies Added

• \cryptography>=41.0\ - Ed25519, AES-GCM encryption
• \mnemonic>=0.20\ - BIP39 seed phrase support

Documentation

• README updated with wallet tool documentation
• Usage examples for all tools
• Security best practices section

Testing

\\�ash
pip install cryptography mnemonic pytest
pytest tests/test_wallet_tools.py -v

24 passed in 6.33s

\\

Bounty Info

• Bounty: #2302 (75 RTC)
• Wallet Address: 9dRRMiHiJwjF3VW8pXtKDtpmmxAPFy3zWgV2JY5H6eeT

Checklist

• Implemented all required wallet tools
• Used Ed25519 signing (via cryptography library)
• Secure keystore storage at ~/.rustchain/mcp_wallets/
• Never expose private keys or seed phrases in responses
• Unit tests for each tool (24 tests, all passing)
• Updated README documentation