chore: add guide on verifying delegate contracts on Etherscan

[igorroncevic]

Summary

Adds a contract verification guide for deploying one dummy Solver7702Delegate per chain, then relying on Etherscan's Similar Match behavior to verify solver EOAs with the same delegate bytecode.

The guide also covers verifying an already deployed delegate, and Foundry now reads one ETHERSCAN_API_KEY for all chains.

Testing

• Run the script from README.md on any chain.

[gemini-code-assist]

Code Review

This pull request adds documentation and scripts for contract verification on Etherscan using a dummy delegate, updates the .gitignore to ignore all broadcast logs, and configures the Etherscan API key in foundry.toml. Feedback focuses on reverting the .gitignore change to preserve production deployment logs, removing the explicit etherscan_api_key configuration in foundry.toml as it breaks local development when the environment variable is missing, and updating the README accordingly.

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