feat: migrate legacy EVM contract suite to legacy/evm (P0-10)

[EKF0]

This PR resolves the repository hygiene gaps surrounding deprecated EVM smart contracts (P0-10).

Changes:

• Relocated EVM assets: Moved Solidity contracts, Hardhat config, and JS tests to a dedicated legacy/evm/ directory.
• Decoupled primary testing pipeline: Updated package.json to make Solana-native Vitest the default test suite (run via npm run test or npm test).
• Preserved legacy testing capability: Enabled isolated, self-contained running of legacy EVM tests using a new command npm run test:evm.
• Refreshed Documentation: Updated ARCHITECTURE.md to reflect the Solana-primary testing architecture, and created legacy/evm/README.md to clarify deprecation status and setup steps.

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[supabase]

This pull request has been ignored for the connected project zgqlbqmebjnsaxraqwmt because there are no changes detected in supabase directory. You can change this behaviour in Project Integrations Settings ↗︎.

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