GH-623: Direct Node to pick new public key on the command line

[dnwiebe]

Note

Medium Risk
Touches startup configuration and persistent key selection logic; incorrect handling could cause nodes to fail to start or unexpectedly rotate identity keys, though changes are gated behind a new explicit flag and covered by tests.

Overview
Adds --new-public-key (and MASQ_NEW_PUBLIC_KEY/config-file support) to let operators explicitly reuse the previously stored public key (off) or force generation and persistence of a new one (on) during startup.

Plumbs this flag through bootstrapping/config parsing (BootstrapperConfig.new_public_key_opt, shared OnOff enum, setup reporter UI defaults) and updates cryptographic key initialization to honor the choice, including hard-fail cases when off is requested but no prior key or --db-password is available.

Integration tests were refreshed to use www.testingmcafeesites.com endpoints/content and improved a bookkeeping assertion for clearer mismatch diagnostics; additionally, config init now returns structured errors on unknown CLI args, and .gitignore now ignores JetBrains Copilot files.

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