[Zig] Fully expose Signers module

[roninjin10]

Summary

Fully expose Signers module in Zig crypto to match TypeScript implementation.

TS Exports to Match

• PrivateKeySigner - Sign with raw private key
• sign - Sign message/transaction
• signTypedData - EIP-712 typed data signing
• signTransaction - Transaction signing
• getAddress - Get signer address

Current State

Zig has signers.zig but not fully exposed in crypto root.zig exports.

Priority

High - Core signing functionality

Note: Issue created by Claude AI assistant, not @roninjin10 or @fucory