refactor(LocalDataSource, PostRepository, ChatScreen): enhance database handling and message loading

- Introduced a promise-based initialization mechanism in LocalDataSource to prevent concurrent initialization issues.
- Updated PostRepository to utilize an enqueueWrite method for database operations, ensuring thread-safe writes.
- Refactored ChatScreen to improve message loading logic, including preloading history and managing scroll behavior more effectively.
- Enhanced message rendering logic to maintain correct indices in inverted lists and optimize user experience during scrolling.

src/stores/messageManager.ts

@@ -287,6 +287,29 @@ class MessageManager {
     return Array.from(merged.values()).sort((a, b) => a.seq - b.seq);
   }
 
+  /**
+   * 历史消息合并优化：
+   * - 常见场景：incoming 全部比 existing 更旧，直接前插，避免全量排序
+   * - 异常/重叠场景：回退到通用 mergeMessagesById
+   */
+  private mergeOlderMessages(existing: MessageResponse[], incoming: MessageResponse[]): MessageResponse[] {
+    if (incoming.length === 0) return existing;
+
+    const incomingAsc = [...incoming].sort((a, b) => a.seq - b.seq);
+    if (existing.length === 0) return incomingAsc;
+
+    const existingMinSeq = existing[0]?.seq ?? Number.MAX_SAFE_INTEGER;
+    const incomingMaxSeq = incomingAsc[incomingAsc.length - 1]?.seq ?? Number.MIN_SAFE_INTEGER;
+
+    // 纯历史前插快路径：避免全量 merge + sort
+    if (incomingMaxSeq < existingMinSeq) {
+      return [...incomingAsc, ...existing];
+    }
+
+    // 兜底：存在重叠/乱序时走通用路径
+    return this.mergeMessagesById(existing, incomingAsc);
+  }
+
   private updateConversationList() {
     // 会话排序：置顶优先，再按最后消息时间排序
     const list = Array.from(this.state.conversations.values()).sort((a, b) => {
@@ -1513,7 +1536,8 @@ class MessageManager {
 
       if (localMessages.length >= limit) {
         // 本地有足够数据
-        const formattedMessages: MessageResponse[] = localMessages.map(m => ({
+        // 本地查询是 seq DESC，这里转成 ASC，匹配渲染时间序
+        const formattedMessages: MessageResponse[] = [...localMessages].reverse().map(m => ({
           id: m.id,
           conversation_id: m.conversationId,
           sender_id: m.senderId,
@@ -1525,7 +1549,7 @@ class MessageManager {
 
         // 合并到现有消息
         const existingMessages = this.state.messagesMap.get(conversationId) || [];
-        const mergedMessages = this.mergeMessagesById(existingMessages, formattedMessages);
+        const mergedMessages = this.mergeOlderMessages(existingMessages, formattedMessages);
         this.state.messagesMap.set(conversationId, mergedMessages);
 
         this.notifySubscribers({
@@ -1561,7 +1585,7 @@ class MessageManager {
 
         // 合并消息
         const existingMessages = this.state.messagesMap.get(conversationId) || [];
-        const mergedMessages = this.mergeMessagesById(existingMessages, serverMessages);
+        const mergedMessages = this.mergeOlderMessages(existingMessages, serverMessages);
         this.state.messagesMap.set(conversationId, mergedMessages);
 
         this.notifySubscribers({