Migrate post-related operations from direct service/store calls to a new use case architecture featuring differential updates. Key changes include: (1) introduce ProcessPostUseCase to handle like, unlike, favorite, unfavorite, delete, and fetch operations with proper state management, (2) add useDifferentialPosts hook for efficient list rendering with minimal re-renders, (3) add PostDiffCalculator and PostUpdateBatcher in infrastructure layer for incremental updates, (4) deprecate NotificationItem component in favor of SystemMessageItem, (5) remove deprecated interactive methods from userStore, (6) add posts_cache table to local datasource, (7) clean up legacy MessageDTO and ConversationDTO types, (8) remove deprecated hook useBreakpointCheck, (9) refactor MessageBubble to use measureInWindow directly for better React Native compatibility
