[kosisochukwu1234]

Description

Resolves an issue where GET /audit-logs was unreachable (returning 404 on the running Express server) because auditLogsRouter was defined in apps/backend/src/routes/auditLogs.ts but never mounted in apps/backend/src/app.ts.

Summary of Changes:

1. Mount Route: Mounted app.use('/audit-logs', auditLogsRouter) in apps/backend/src/app.ts after the global rate limiter and security router.
2. Rate Limiting: Added audit_logs bucket (30 / min) to apps/backend/src/config/rateLimits.ts and attached rateLimit('audit_logs') to auditLogsRouter.
3. Query Parsing: Replaced hand-parsed action, limit, and cursor query parameters with AuditLogsQuerySchema (using Zod) while preserving existing 400 response formats for unknown action filters.
4. Docs & Tests: Documented the new rate limit bucket in docs/security/rate-limits.md and added a test in apps/backend/src/__tests__/auditLog.test.ts requesting /audit-logs through app to verify reachability.

Closes #648