Fix undefined $node_version on hosts without Node, plus cleanup

[xpersonas]

• Default node_version to null so the endpoint no longer 500s when Node isn't installed (e.g. AWS Lambda)
• Compare API keys with hash_equals(); return 401 for a missing request key and 500 only when the key isn't configured
• Rate limit the endpoint to 60 requests per minute
• Report the installed package version in php artisan about
• Remove the unregistered StackReporter facade, unused guzzle dependency and unused InstalledVersions constructor argument
• Move laravel/framework to require; bump testbench to ^9.0|^10.0
• Rewrite the stale test suite and update CI to PHP 8.2-8.4 x Laravel 11/12
• Update README to match the code; backfill CHANGELOG; add .gitignore

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Technical Description