574bcf2264
- Add ioredis dependency for Redis connection pooling - Create RedisService singleton with connection management - Add Redis config (url, dedupWindowSeconds) to notification.config.ts - Implement NotificationService.checkRateLimit using Redis INCR+EXPIRE - Implement NotificationService.deduplicateNotification using Redis SET/NX - Add configurable rate limit windows and thresholds via env vars - Add 29 unit tests covering Redis operations, rate limiting, and dedup - All tests pass, TypeScript compiles cleanly for new files