feat(db): add getLastMessageByConversation and update conversation list preview

Add `getLastMessageByConversation` to `MessageRepository` to allow fetching the most recent message for a specific conversation.

Update `ConversationListRow` to use this new repository method as a fallback when message segments are missing, ensuring the conversation list preview displays the last message content correctly.

src/screens/message/components/ConversationListRow.tsx

@@ -14,7 +14,7 @@ import {
   MessageSegment,
 } from '../../../types/dto';
 import { authService } from '../../../services';
-import { userCacheRepository } from '@/database';
+import { userCacheRepository, messageRepository } from '@/database';
 import { Avatar, Text } from '../../../components/common';
 
 const AnimatedTouchable = Animated.createAnimatedComponent(TouchableOpacity);
@@ -34,7 +34,8 @@ const AsyncMessagePreview: React.FC<{
   status?: string;
   isGroupChat?: boolean;
   senderName?: string;
-}> = ({ segments, status, isGroupChat, senderName }) => {
+  conversationId?: string;
+}> = ({ segments, status, isGroupChat, senderName, conversationId }) => {
   const [displayText, setDisplayText] = useState<string>('');
   const isMountedRef = useRef(true);
 
@@ -49,19 +50,33 @@ const AsyncMessagePreview: React.FC<{
         return;
       }
 
-      const initialText = extractTextFromSegments(segments);
+      let effectiveSegments = segments;
+
+      // 当 segments 为空时，从本地 SQLite 回退查询
+      if ((!effectiveSegments || effectiveSegments.length === 0) && conversationId) {
+        try {
+          const lastMsg = await messageRepository.getLastMessageByConversation(conversationId);
+          if (lastMsg?.segments) {
+            effectiveSegments = Array.isArray(lastMsg.segments)
+              ? lastMsg.segments
+              : JSON.parse(lastMsg.segments);
+          }
+        } catch {}
+      }
+
+      const initialText = extractTextFromSegments(effectiveSegments);
       if (isMountedRef.current) {
         setDisplayText(initialText);
       }
 
-      const hasAtWithoutNickname = segments?.some(
+      const hasAtWithoutNickname = effectiveSegments?.some(
         (s) => s.type === 'at' && s.data.user_id !== 'all' && !s.data.nickname
       );
 
       if (hasAtWithoutNickname) {
         try {
           const asyncText = await extractTextFromSegmentsAsync(
-            segments,
+            effectiveSegments,
             userCacheRepository.get.bind(userCacheRepository),
             authService.getUserById.bind(authService)
           );
@@ -79,7 +94,7 @@ const AsyncMessagePreview: React.FC<{
     return () => {
       isMountedRef.current = false;
     };
-  }, [segments, status]);
+  }, [segments, status, conversationId]);
 
   if (!displayText) return null;
 
@@ -363,6 +378,7 @@ const ConversationListRowInner: React.FC<ConversationListRowProps> = ({
                 status={item.last_message?.status}
                 isGroupChat={isGroupChat}
                 senderName={getSenderName()}
+                conversationId={item.id}
               />
             )}
           </Text>