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/stores/messageManagerHooks.ts

@@ -103,6 +103,7 @@ export function useMessages(conversationId: string | null): UseMessagesReturn {
   const [messages, setMessages] = useState<MessageResponse[]>([]);
   const [isLoading, setIsLoading] = useState(false);
   const [hasMore, setHasMore] = useState(true);
+  const loadMoreInFlightRef = useRef(false);
 
   useEffect(() => {
     if (!conversationId) {
@@ -156,23 +157,23 @@ export function useMessages(conversationId: string | null): UseMessagesReturn {
   }, [conversationId]);
 
   const loadMore = useCallback(async () => {
-    if (!conversationId || isLoading || !hasMore) return;
+    if (!conversationId || !hasMore || loadMoreInFlightRef.current) return;
 
     const currentMessages = messageManager.getMessages(conversationId);
     if (currentMessages.length === 0) return;
 
-    // 获取最早的消息seq
-    const minSeq = Math.min(...currentMessages.map(m => m.seq));
+    // 消息数组在 MessageManager 内保持 seq 升序，首项即最早消息
+    const minSeq = currentMessages[0]?.seq ?? Math.min(...currentMessages.map(m => m.seq));
 
-    setIsLoading(true);
+    loadMoreInFlightRef.current = true;
     const loadedMessages = await messageManager.loadMoreMessages(conversationId, minSeq, 20);
-    setIsLoading(false);
+    loadMoreInFlightRef.current = false;
 
     // 如果没有加载到新消息，说明没有更多了
     if (loadedMessages.length === 0) {
       setHasMore(false);
     }
-  }, [conversationId, isLoading, hasMore]);
+  }, [conversationId, hasMore]);
 
   const refresh = useCallback(async () => {
     if (!conversationId) return;