Fix critical bugs, add message signing capabilities and multicall tool

[aaurelions]

Critical Bug Fixes

• Fix parameter order mismatch in approve_token_spending tool
  • Corrected approveERC20 function call arguments
  • This bug prevented token approvals from working
• Fix Buffer compatibility issue in wallet.ts for Bun runtime
  • Replaced Node.js Buffer with platform-agnostic Array conversion
  • Ensures compatibility across Bun and Node.js environments

New Features

• Add message signing service functions (wallet.ts)
  • signMessage(): Sign arbitrary messages for authentication
  • signTypedData(): Sign EIP-712 structured data
• Add sign_message MCP tool
  • Enables SIWE authentication flows
  • Supports off-chain signature verification
• Add sign_typed_data MCP tool
  • Enables gasless transactions via meta-transactions
  • Supports EIP-2612 permit signatures
  • Enables relay service integration

Documentation

• Update README with message signing capabilities section
• Add new tools to API reference (24 tools total, up from 22)
• Document SIWE, permit, and meta-transaction support

These changes enable AI agents to:

• Authenticate using Sign-In With Ethereum (SIWE)
• Create meta-transactions for gasless transfers
• Generate permit signatures for off-chain approvals
• Sign any EIP-712 structured data for dApp integrations

[aaurelions]

Add multicall tool to batch multiple contract read calls into a single RPC request using the Multicall3 contract.

This significantly reduces latency and RPC usage when querying multiple contract functions.

Features:

• Automatic ABI fetching from block explorers for verified contracts
• Fallback to common function signatures (ERC20 standards)
• Partial failure support - returns successful results even if some calls fail
• ENS name support for contract addresses
• Works across all 60+ supported networks

New tool:

• multicall: Batch multiple contract reads in a single call

Use cases:

• Portfolio analysis: Get multiple token balances at once
• Price aggregation: Query multiple DEX prices simultaneously
• Token metadata: Fetch name, symbol, decimals, totalSupply in one call
• Protocol state: Check multiple contract parameters efficiently

Service functions:

• Added multicall() to src/core/services/contracts.ts

Documentation:

• Updated tool count from 24 to 25
• Added multicall usage example with USDC contract
• Added multicall to API reference table

[wayzeek]

@claude please review this PR

[wayzeek]

that looks great so far, thank you ! @aaurelions

[wayzeek]

Excellent, let's get it to merge !
Thank you for your contribution @aaurelions