Migrate Solidity contracts from single-file to modular Hardhat project

[Smartdevs17]

Description

Solidity contracts and tests are scattered in loose files. Migrate to a structured Hardhat project with proper testing, deployment scripts, and Ethers.js integration.

Acceptance Criteria

• Hardhat project structure with contracts/, test/, scripts/
• TypeChain type generation for all contracts
• Deployment scripts with network management
• Test migration to Hardhat test runner
• Gas reporting configuration
• CI integration for Hardhat tests

Technical Scope

• contracts/evm/
• .github/workflows/contracts-evm.yml
• Edge: bytecode verification mismatch, library linking