Etherscan API v2 migration

[Berny-art]

Etherscan has migrated their verification API. I've changed the docs to reflect that api changed.

• Method is verified using both Hardhat and Foundry.
• More information on the migration: https://docs.etherscan.io/v2-migration

[Berny-art]

@jarrodwatts

[cursor]

PR Summary

Low Risk
Docs-only changes that update example verification endpoints and API key placeholders; no runtime or onchain code is affected.

Overview
Documentation updates migrate all contract verification examples/configs from Abscan’s verification API URLs to Etherscan API v2 endpoints (https://api.etherscan.io/v2/api?chainid=...) for both testnet (11124) and mainnet (2741).

Foundry docs update foundry.toml [etherscan] entries and forge create/forge verify-contract commands to pass --verifier etherscan and the new --verifier-url, and they standardize placeholders for user-provided API keys. Hardhat docs similarly update etherscan.customChains apiURL, and the “Connect to Abstract” page updates the listed “Verify URL”.

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