refactor(messages): 替换nut组件为原生view并优化布局样式

使用原生view组件替代nut-row和nut-col，简化布局结构
调整flex布局和间距样式，提升代码可维护性

@@ -43,8 +43,8 @@
             <view v-for="conversation in filteredConversations" :key="conversation.id"
                 class="conversation-item mt-2 mb-4 border-b border-gray-100 pb-2"
                 @click="onConversationClick(conversation)">
-                <nut-row>
-                    <nut-col :span="6" class="avatar-container">
+                <view class="flex items-start">
+                    <view class="avatar-container flex-shrink-0">
                         <view class="relative">
                             <image v-if="conversation.type === 'chat'" :src="conversation.avatar || defaultAvatar"
                                 class="w-12 h-12 rounded-full object-cover" mode="aspectFill" />
@@ -52,10 +52,10 @@
                                 <component :is="conversation.icon" />
                             </view>
                         </view>
-                    </nut-col>
-                    <nut-col :span="20" class="content-container">
+                    </view>
+                    <view class="content-container flex-1 min-w-0">
                         <view class="flex justify-between items-center mb-1">
-                            <text class="font-medium truncate flex-1 mr-2">{{ conversation.name }}</text>
+                            <text class="font-medium flex-1 mr-2 truncate">{{ conversation.name }}</text>
                             <view class="flex items-center flex-shrink-0">
                                 <text class="text-xs text-gray-500">{{ conversation.time }}</text>
                                 <view v-if="conversation.unread" class="ml-1 bg-red-500 rounded-full w-2 h-2">
@@ -63,8 +63,8 @@
                             </view>
                         </view>
                         <text class="text-sm text-gray-600 truncate block">{{ conversation.lastMessage }}</text>
-                    </nut-col>
-                </nut-row>
+                    </view>
+                </view>
             </view>
 
             <!-- 空状态提示 -->
@@ -528,14 +528,15 @@ onUnmounted(() => {
     }
 
     .avatar-container {
-        display: flex;
-        align-items: flex-start;
         width: 88rpx;
         margin-right: 24rpx;
+        flex-shrink: 0;
     }
 
     .content-container {
-        padding-left: 8px;
+        flex: 1;
+        min-width: 0;
+        padding-left: 8rpx;
     }
 
     .conversation-item:active {