[Zig] Implement Contract utilities module

[roninjin10]

Summary

Implement Contract utilities module in Zig to match TypeScript.

Required Features

Contract Interface

• ABI parsing and encoding
• Function call encoding
• Result decoding
• Event log parsing

Contract Deployment

• Deploy transaction creation
• Constructor argument encoding
• Bytecode + args concatenation

Contract Interaction

• encodeFunctionCall - Encode function with args
• decodeFunctionResult - Decode return values
• encodeEventTopics - Encode event filter topics
• decodeEventLog - Decode event from log

Utilities

• Function selector calculation
• Event topic calculation
• Error decoding

Current State

No contract utilities module in Zig.

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