Fix: stop register-super failing against a running app (fixes #123)

[taylortom]

Fixes #123

Fix

• Extract the "is the app already listening?" probe out of registerSuperUser into lib/utils/isAppRunning.js, and treat any HTTP response as proof the app is running — including an error status. The probe requests the API endpoint map, which requires authentication, so an unauthenticated probe against a live instance gets a 401 rather than a 200. The old code only tolerated ECONNREFUSED and rethrew everything else, so register-super aborted with MISSING_AUTH_HEADER (401) before reaching auth/local/registersuper.
• Only a refused connection now means "not listening" and triggers startApp(). Errors that are neither a response nor a refused connection (a missing conf file, an unreachable host) still propagate, so genuine misconfiguration isn't swallowed into a spurious in-process boot.

Testing

• New tests/isAppRunning.spec.js covering all six branches: success, a 401, other error statuses, ECONNREFUSED, a non-transport error, and a non-ECONNREFUSED transport error.
• Full suite passes (182 tests), standard clean.

[github-actions]

🎉 This PR is included in version 1.2.2 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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