fix: normalize address in sim_fundAccount

[feafel]

Summary

Fixes #1788: sim_fundAccount returned a success-looking result hash but silently credited nothing when passed a lowercase address (e.g. from MetaMask). Ethereum JSON-RPC addresses are case-insensitive, so normalize to checksum format before the lookup.

Changes

• backend/protocol_rpc/endpoints.py: added to_checksum_address normalization after address validation
• tests/unit/test_simulator_sessions.py: added test for lowercase address normalization

Impact

Wallets such as MetaMask return lowercase addresses from eth_accounts, so a faucet button that passes the connected address silently did nothing. Now the address is properly normalized before crediting.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Account funding now stores valid addresses in a consistent checksum format, including when lowercase addresses are provided. Invalid addresses continue to be rejected.

[github-actions]

This PR targeted main, which is only the default/static branch.

I retargeted it to v0.123-dev, the active development branch. Pushes to v0.123-dev automatically fast-forward main.

[coderabbitai]

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