refactor(post): consolidate post sync to PostSyncService and remove ProcessPostUseCase

- Replace ProcessPostUseCase with new PostSyncService in src/services/post/
- Add postListStore for state management in src/stores/post/
- Remove deprecated ProcessPostUseCase and ProcessMessageUseCase files
- Delete architecture documentation files (ARCHITECTURE_REFACTOR_PLAN.md, architecture-comparison-report.md)
- Update all consumers (HomeScreen, PostDetailScreen, SearchScreen, useUserProfile, useDifferentialPosts)
- Simplify postService to only contain API layer methods
- Remove unused type exports from message stores

BREAKING CHANGE: ProcessPostUseCase and ProcessMessageUseCase have been removed.
Use postSyncService for post operations instead.

src/stores/message/MessageManager.ts

@@ -29,9 +29,6 @@ import { useMessageStore, normalizeConversationId } from './store';
 
 // 重新导出类型，保持兼容性
 export type {
-  MessageEventType,
-  MessageEvent,
-  MessageSubscriber,
   MessageManagerState,
   ReadStateRecord,
   MessageManagerConversationListDeps,