[LOW] Redact private JWK material from inspection

[OskarEichler]

Summary

Prevents routine inspection and pretty-printing of JWK objects from exposing private cryptographic parameters. This addresses finding 4 in #723.

Problem

Ruby's default object inspection includes instance variables. JWT::JWK::KeyBase stores complete JWK parameters in @parameters, including:

• HMAC secret k
• RSA private values d, p, q, dp, dq, and qi
• EC private value d

Logging, debugging, or pretty-printing a private JWK therefore emits private key material.

Fix

Implement inspect and pretty_print in KeyBase using each concrete JWK type's existing default export. That export already retains public metadata while omitting private cryptographic parameters.

Verification

• Focused reproduction before: HMAC, RSA, and EC private values all appeared in both inspect and PP.pp
• Focused reproduction after: all six checks report redacted
• bundle exec rspec: 557 examples, 0 failures, 12 expected pending
• bundle exec rubocop lib/jwt/jwk/key_base.rb: no offenses
• Ruby syntax check: successful
• Ruby 4.0.6, OpenSSL 3.6.0/3.6.3

No test files are included in this focused patch. The behavior was verified with an external reproduction plus the complete existing suite.

Compatibility

The textual representation of JWK objects changes. Public JWK parameters remain visible; private cryptographic parameters no longer do. No runtime signing, verification, import, or export API behavior changes. No breaking change intended.

[anakinj]

pp is not a dependency of the gem so i would drop this method.

[anakinj]

A spec to test this would be useful. also maybe not claim @parameters equals the exported value as its not really true.

[anakinj]

@OskarEichler This looks promising. Could you take a look at my comments and adjust?