refactor: use utility helpers consistently across codebase

refactor: use utility helpers consistently across codebase

Replace manual * 1000 with secondsToMilliseconds() in auth
cache, remote strategy, and OCPP20 incoming request. Replace
manual / 1000 with millisecondsToSeconds() in auth helpers,
auth service, and cert signing retry. Replace 'in' operator
with has() in auth service. Replace configurationKey find
with getConfigurationKey() in OCPP20RequestService. Use
formatDurationMilliSeconds for reconnect delay log. Keep
ms precision in auth service logs (sub-second durations).