把“章节正文 + 图片”从 chapters 单表/JSON 结构，重构为“章节 chapter + 段落 section + 图片 memoir_images 独立表”的新数据模型，同时联动修改接口、PDF 导出、异步任务、迁移脚本、测试，以及修复 Android 端聊天列表显示问题。 (#9)

* refactor: 表结构重构，新增段落section和图片image新表

* fix: fix android app import error

* refactor: 重构文件名

* fix: 优化提示词

* fix: 消息气泡显示位置异常问题

---------

Co-authored-by: yangshilin <2157598560@qq.com>

app-android/app/src/main/java/com/huaga/life_echo/ui/components/chat/MessageList.kt

@@ -13,7 +13,6 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.key
-import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
@@ -91,54 +90,30 @@ fun MessageList(
         count
     }
 
-    // 当前对话是否已加载过消息（用于首次显示时直接定位到底部，避免从顶部再滑到底部）
-    var hasReceivedMessages by remember(conversationId) { mutableStateOf(false) }
-    LaunchedEffect(conversationId, messages) {
-        if (messages.isNotEmpty()) hasReceivedMessages = true
+    val listState = key(conversationId) {
+        rememberLazyListState()
     }
 
-    // 用 key 在「首次有消息」时重建列表状态，使 initialFirstVisibleItemIndex 生效，打开对话即显示底部
-    val initialIndex = if (hasReceivedMessages && estimatedItemCount > 0) (estimatedItemCount - 1).coerceAtLeast(0) else 0
-    val listState = key(conversationId, hasReceivedMessages) {
-        rememberLazyListState(initialFirstVisibleItemIndex = initialIndex, initialFirstVisibleItemScrollOffset = 0)
-    }
-
-    // 自动滚动到底部 - 当消息变化或流式内容更新时滚动
+    // reverseLayout 下 index 0 在视口底部，scrollToItem(0) 即显示最新内容
     LaunchedEffect(messages.size, messages.lastOrNull()?.id, isStreaming, streamingText, isTyping) {
-        // 短暂延迟确保内容已渲染
+        if (estimatedItemCount <= 0) return@LaunchedEffect
         delay(100)
-        
-        // 滚动到最后一项
-        if (estimatedItemCount > 0) {
-            try {
-                listState.animateScrollToItem(estimatedItemCount - 1)
-            } catch (e: Exception) {
-                // 如果索引超出范围，尝试滚动到实际的最后一项
-                val actualCount = listState.layoutInfo.totalItemsCount
-                if (actualCount > 0) {
-                    listState.animateScrollToItem(actualCount - 1)
-                }
-            }
-        }
+        try {
+            listState.animateScrollToItem(0)
+        } catch (_: Exception) { }
     }
     
     LazyColumn(
         state = listState,
+        reverseLayout = true,
         modifier = modifier
             .fillMaxSize()
             .onSizeChanged { size ->
                 val h = size.height
-                // 键盘弹出导致列表高度变矮时，滚到最底部，让最后一条气泡紧贴输入框上方
                 if (lastHeightPx > 0 && h < lastHeightPx) {
                     scope.launch {
                         delay(80)
-                        val count = listState.layoutInfo.totalItemsCount
-                        if (count > 0) {
-                            val viewportHeight = listState.layoutInfo.viewportSize.height
-                            // 一次平滑滚到底：用 scrollOffset 让最后一项贴底，避免两段滚动和中间停顿
-                            val scrollOffset = (viewportHeight - 120).coerceAtLeast(0)
-                            listState.animateScrollToItem(count - 1, scrollOffset)
-                        }
+                        listState.animateScrollToItem(0)
                     }
                 }
                 lastHeightPx = h
@@ -146,16 +121,30 @@ fun MessageList(
         contentPadding = PaddingValues(vertical = 8.dp),
         verticalArrangement = Arrangement.spacedBy(4.dp)
     ) {
-        // 时间分隔线
+        // reverseLayout: 先添加的显示在底部。顺序：typing(底) -> streaming -> messages(新->旧)
+        if (isTyping || (isStreaming && streamingText.isEmpty())) {
+            item { TypingIndicator() }
+        }
+        if (isStreaming) {
+            val streamingParts = streamingText.split("[SPLIT]").map { it.trim() }.filter { it.isNotEmpty() }
+            if (streamingParts.size > 1) {
+                streamingParts.dropLast(1).forEachIndexed { partIndex, part ->
+                    item(key = "streaming_complete_$partIndex") { AIMessageBubble(text = part) }
+                }
+                item(key = "streaming_message") { StreamingAIMessageBubble(text = streamingParts.last()) }
+            } else {
+                item(key = "streaming_message") { StreamingAIMessageBubble(text = streamingText) }
+            }
+        }
+        // 历史消息：从新到旧，最新在底部
         var lastDate: Long? = null
-        
-        messages.forEachIndexed { index, message ->
+        messages.asReversed().forEachIndexed { index, message ->
             val currentDate = message.timestamp
-            val shouldShowDivider = lastDate == null || 
-                    (currentDate - lastDate!!) > 300000 // 5分钟间隔
+            // 反向迭代：lastDate 是更新的消息，间隔>5分钟显示分隔线
+            val shouldShowDivider = index > 0 && lastDate != null && (lastDate!! - currentDate) > 300000
             
-            if (shouldShowDivider && index > 0) {
-                item {
+            if (shouldShowDivider) {
+                item(key = "divider_${message.id}") {
                     TimeDivider(timestamp = currentDate)
                 }
             }
@@ -228,40 +217,6 @@ fun MessageList(
             
             lastDate = currentDate
         }
-        
-        // 流式消息显示 - 使用专门的流式消息气泡组件
-        // 在 [SPLIT] 处分割流式消息
-        if (isStreaming) {
-            val streamingParts = streamingText.split("[SPLIT]")
-                .map { it.trim() }
-                .filter { it.isNotEmpty() }
-            
-            if (streamingParts.size > 1) {
-                // 已完成的部分显示为普通气泡
-                streamingParts.dropLast(1).forEachIndexed { partIndex, part ->
-                    item(key = "streaming_complete_$partIndex") {
-                        AIMessageBubble(text = part)
-                    }
-                }
-                // 最后一部分显示为流式气泡（可能还在输入）
-                item(key = "streaming_message") {
-                    StreamingAIMessageBubble(text = streamingParts.last())
-                }
-            } else {
-                item(key = "streaming_message") {
-                    StreamingAIMessageBubble(text = streamingText)
-                }
-            }
-        }
-        
-        // 正在输入指示器 - 显示加载动画
-        // 1. 如果正在流式接收但还没有内容，显示加载动画
-        // 2. 如果设置了isTyping且不在流式状态，显示加载动画
-        if (isTyping || (isStreaming && streamingText.isEmpty())) {
-            item {
-                TypingIndicator()
-            }
-        }
     }
 }