Package-level declarations

Checks the backend's current cache version against the locally cached one, invalidating stale cached screens/graph if they don't match — run once at app startup by MosaicApplicationStateHolder, before dev.catbit.mosaic.client.domain.graph.GetInitialGraphUseCase fetches the initial graph, so a stale cache never serves an outdated graph. Reachable via get<CheckCacheVersionUseCase>().