refactor(ProcessPostUseCase, useCursorPagination, useDifferentialPosts): enhance post merging and loading states

- Introduced new methods for merging posts and comments efficiently, improving performance during data updates.
- Updated loading state management in hooks to include initial loading and loading more states for better user feedback.
- Refactored HomeScreen and PostDetailScreen to utilize the new loading states and merging logic, enhancing user experience during data fetching.
- Improved pagination handling in useCursorPagination and useDifferentialPosts to ensure consistent data management across components.

src/infrastructure/pagination/types.ts

@@ -214,6 +214,10 @@ export interface CursorPaginationState<T> {
   hasMore: boolean;
   /** 是否正在加载 */
   isLoading: boolean;
+  /** 是否首屏加载（空列表初始化） */
+  isInitialLoading: boolean;
+  /** 是否正在加载更多 */
+  isLoadingMore: boolean;
   /** 是否正在刷新 */
   isRefreshing: boolean;
   /** 错误信息 */