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/screens/home/SearchScreen.tsx

@@ -20,6 +20,7 @@ import { spacing, fontSizes, borderRadius, useAppColors, type AppColors } from '
 import { Post, User } from '../../types';
 import { useUserStore } from '../../stores';
 import { postService, authService } from '../../services';
+import { postSyncService } from '../../services/post/PostSyncService';
 import { PostCard, TabBar, SearchBar } from '../../components/business';
 import type { PostCardAction } from '../../components/business/PostCard';
 import { Avatar, EmptyState, Text, ResponsiveGrid, Loading } from '../../components/common';
@@ -185,19 +186,19 @@ export const SearchScreen: React.FC<SearchScreenProps> = ({ onBack }) => {
         }
         break;
       case 'like':
-        postService.likePost(post.id);
+        postSyncService.likePost(post.id);
         break;
       case 'unlike':
-        postService.unlikePost(post.id);
+        postSyncService.unlikePost(post.id);
         break;
       case 'comment':
         handlePostPress(post.id, true);
         break;
       case 'bookmark':
-        postService.favoritePost(post.id);
+        postSyncService.favoritePost(post.id);
         break;
       case 'unbookmark':
-        postService.unfavoritePost(post.id);
+        postSyncService.unfavoritePost(post.id);
         break;
       case 'share':
         // 搜索页暂不处理分享