perf(auth): cache key length properties

[Fdawgs]

Caching the key property is a teeny bit faster as it's not having to do property access.

See https://github.com/kibertoad/nodejs-benchmark-tournament/blob/master/loops/_results/results.md

Checklist

• run npm run test && npm run benchmark --if-present
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[Copilot]

Pull request overview

This PR implements a micro-optimization to improve loop performance in the auth function by caching array length properties in local variables before iteration, avoiding repeated property access during loop condition checks.

• Caches functions.length before the outer loop
• Caches functions[i].length before each inner loop iteration

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[gurgunday]

lgtm