Add Key Check Value operation

[J8k3]

Summary

Adds a Key Check Value operation to the Hashing category. A KCV is a short public value derived from a symmetric key so two parties can verify they hold the same key without exposing it — widely used in payment HSM key management (TR-31 / ANSI X9.143 KC blocks) and general symmetric-key handling.

Three standard methods:

• TDES-ECB (Zeros) — ANSI X9.24-1 legacy KCV
• AES-ECB (Zeros) — AES analogue of the same construction
• AES-CMAC (Empty) — RFC 4493 CMAC of the empty message, per TR-31

Returns the leading N hex characters of the resulting cryptogram (default 6, matching typical KCV length).

Notes

• No new dependencies: uses existing node-forge and the in-tree CMAC operation.
• 3 files changed / 215 lines added — one op file, one test file, one Categories.json entry.
• Test vectors sourced from NIST SP 800-67 Rev 2 §B.1 (TDES) and NIST SP 800-38B Appendix D.1 (AES), and cross-corroborated against the existing CMAC test suite.

Test plan

• npm test — all 7 KCV tests pass; no regressions in adjacent ops.
• npx eslint — clean.
• Op runs manually across each method and error path.