feat(listings): rate limit feature-listing via @nestjs/throttler (TEC-2930)

- Wire ThrottlerModule to a Redis-backed storage (shared across API
  instances) using @nest-lab/throttler-storage-redis.
- Add FeatureListingThrottlerGuard that tracks per-user when JWT is
  present, falling back to the real client IP behind the reverse proxy —
  keeps per-user and per-IP buckets independent.
- Apply @Throttle({ default: { limit: 10, ttl: 60_000 } }) + the guard
  to POST /listings/:id/feature and document 429 in Swagger.
- Integration test (feature-listing-throttle.integration.spec.ts)
  verifies: 10 reqs pass / 11th returns 429 with Retry-After, separate
  IPs keep their own quotas, and the tracker key logic.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/modules/shared/infrastructure/index.ts

@@ -22,6 +22,7 @@ export { SanitizeInputMiddleware } from './middleware/sanitize-input.middleware'
 export { CsrfMiddleware } from './middleware/csrf.middleware';
 export { maskPii } from './pii-masker';
 export { ThrottlerBehindProxyGuard } from './guards/throttler-behind-proxy.guard';
+export { FeatureListingThrottlerGuard } from './guards/feature-listing-throttler.guard';
 export {
   UserRateLimitGuard,
   DEFAULT_ROLE_LIMITS,