fix: cache remote JWK Set instances to reduce redundant JWKS requests

[xiaoyijun]

Summary

Previously, TokenVerifier.createVerifyJwtFunction created a new createRemoteJWKSet instance on every token verification call. This caused jose's internal caching mechanisms (cooldownDuration, cacheMaxAge) to be ineffective, resulting in redundant HTTP requests to the JWKS endpoint.

This PR caches the remote JWK Set instances by JWKS URI, allowing jose's built-in caching to work as intended:

• 30-second cooldown between requests
• 10-minute cache max age
• Automatic key rotation handling when no matching key is found

Closes #42

Testing

unit tests

Checklist

• .changeset
• unit tests
• integration tests
• necessary TSDoc comments

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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