Add AWS Comprehend PII redaction utility

[nguyenduchuyhd]

/claim #290

Summary:

• Add AwsComprehendRedactor to the JS AI package using AWS Comprehend DetectPiiEntities.
• Redact plain text, prompt inputs, and chat message arrays before passing them to existing endpoint classes.
• Export the utility from @arakoodev/edgechains.js/ai, add a usage example, and cover masking/filtering behavior with tests.

Verification:

• npx vitest run src/ai/src/tests/awsComprehendRedactor.test.ts
• npx tsc -b

[github-actions]

CLA Assistant Lite bot: Thank you for your submission, we really appreciate it. Before we can accept your contribution, we ask that you sign the Arakoo Contributor License Agreement. You can sign the CLA by adding a new comment to this pull request and pasting exactly the following text.

---

I have read the Arakoo CLA Document and I hereby sign the CLA

---

_{You can retrigger this bot by commenting recheck in this Pull Request}