feat(audit): add authorized structured vault operation history

[Jagadeeshftw]

Summary

• Adds versioned, structured audit events for privileged vault operations.
• Records actor, role, action, target, correlation ID, outcome, and bounded redacted metadata.
• Adds admin/auditor authorization, filters, pagination, and deposit/withdraw lifecycle instrumentation.
• Documents schema, persistence, redaction, incident response, and deployment controls.

Validation

• npm test — 59 passing
• git diff --check — clean
• Diff size: 501 changed lines

Issue

Closes #72