refactor(ocpp2): integrate InMemoryAuthCache into auth service

refactor(ocpp2): integrate InMemoryAuthCache into auth service

Update factory, interfaces, and service to support cache integration:
- AuthComponentFactory.createAuthCache() now instantiates InMemoryAuthCache
- Add evictions field to CacheStats interface
- Add rateLimit field to AuthStats interface (blockedRequests, rateLimitedIdentifiers, totalChecks)
- Make OCPPAuthServiceImpl.getStats() async to fetch cache stats from strategies
- Update factory test to expect cache instance

Enables monitoring of cache evictions and rate limiting events.