[boluxx123]

Overview

This PR adds structured audit logging for destructive admin actions and authentication outcomes. Successful admin reset/replay operations now emit an audit entry capturing the actor's publicKey, action, params, and requestId, and verifyChallenge / requireAdmin log auth success and admin grant/deny with the publicKey — without leaking secrets or tokens.

Related Issue

Changes

🔐 Audit Logging Helper

• [MODIFY] backend/src/logger.ts
  • Adds a small structured audit-log helper that emits consistent entries (actor publicKey, action, params, requestId) and strips/omits sensitive fields so no secrets or tokens land in the audit trail.

🛡️ Admin Route Audit Entries

• [MODIFY] backend/src/routes/v1/admin.routes.ts
  • Successful reset/replay endpoints now emit a structured audit entry with the actor's publicKey, the action, the params passed, and the requestId — previously only the failure path was logged.

🔑 Auth & Admin Grant/Deny Logging

• [MODIFY] backend/src/middleware/auth.ts
  • verifyChallenge logs auth success with the publicKey (error path already logged).
  • requireAdmin logs admin grant/deny with the publicKey.

🧪 Tests

• [MODIFY] backend/tests/auth.test.ts
  • Covers auth success logging and admin grant/deny logging with publicKey.
• [MODIFY] backend/tests/integration/reset-replay-race.test.ts
  • Covers audit entries for successful reset/replay under concurrent requests.

Verification Results

npm test -- backend/tests/auth.test.ts backend/tests/integration/reset-replay-race.test.ts
✅ tests passed

npm run lint
✅ no errors

Acceptance Criteria	Status
Successful admin reset/replay emits a structured audit log entry (actor publicKey, action, params, requestId)	✅ Audit entry emitted on success in admin.routes.ts
verifyChallenge logs auth success, and requireAdmin logs grant/deny with the publicKey	✅ Logged in auth.ts
Audit entries are checked to be free of secrets/tokens	✅ Helper omits sensitive fields; covered by tests
tests + lint pass, CI green	✅ Tests and lint pass locally

Closes #824