[Bounty] RustChain MCP Server v0.4: Wallet Management + Transfer Tools (75 RTC)

## Bounty: 75 RTC ### Description Extend the RustChain MCP Server (https://github.com/Scottcjn/rustchain-mcp) with wallet management and signed transfer capabilities. Currently the MCP server has 25 tools — add wallet operations so any MCP-compatible AI agent can manage RTC programmatically. ### New Tools Required - `wallet_create` — generate new Ed25519 wallet with BIP39 seed phrase - `wallet_balance` — check balance for any wallet ID - `wallet_history` — transaction history for a wallet - `wal