feat(messaging): implement optimistic updates with retry for failed messages

- Add pending/failed message status to track send state
- Implement optimistic UI: show message immediately, update on server response
- Add retry functionality for failed messages via tap-to-retry
- Change send button from icon to text "发送" for clarity
- Add MessageSendService with temp ID generation to prevent collisions

feat(notification): add JPush notification deduplication and clear on tap

- Deduplicate notificationArrived events from dual JPush/vendor channels
- Clear all notifications on tap (QQ-style behavior)

feat(post): add client-side idempotency key for post creation

- Generate client_request_id per publish intent to prevent duplicates on retry
- Pass idempotency key through to postService and voteService

src/screens/home/HomeScreen.tsx

@@ -795,7 +795,7 @@ export const HomeScreen: React.FC = () => {
     const authorId = item.author?.id || '';
     const isPostAuthor = currentUser?.id === authorId;
     return (
-      <View style={{ marginBottom: 2, paddingHorizontal: 1 }}>
+      <View style={{ marginBottom: 2, paddingHorizontal: responsiveGap / 2 }}>
         <PostCard
           post={item}
           variant="grid"
@@ -804,7 +804,7 @@ export const HomeScreen: React.FC = () => {
         />
       </View>
     );
-  }, [currentUser?.id, stableOnPostAction]);
+  }, [currentUser?.id, stableOnPostAction, responsiveGap]);
 
   // 渲染响应式网格布局（所有端统一使用 FlashList masonry 模式）
   const renderResponsiveGrid = () => {
@@ -820,7 +820,7 @@ export const HomeScreen: React.FC = () => {
         masonry
         optimizeItemArrangement
         contentContainerStyle={{
-          paddingHorizontal: responsivePadding,
+          paddingHorizontal: responsiveGap / 2,
           paddingBottom: 80 + responsivePadding,
         }}
         showsVerticalScrollIndicator={false}

src/screens/home/PostDetailScreen.tsx

@@ -1358,21 +1358,15 @@ export const PostDetailScreen: React.FC = () => {
     );
   }, [currentUser?.id, handleDeleteComment, handleImagePress, handleLikeComment, handleLoadMoreReplies, post?.user_id, handleReportComment]);
 
-  // 渲染空评论 - 类似图片中的样式
+  // 渲染空评论 - 使用 Forum 图标
   const renderEmptyComments = useCallback(() => (
     <View style={styles.emptyCommentsContainer}>
-      {/* 四个方块图标 */}
-      <View style={styles.emptyCommentsGrid}>
-        <View style={styles.emptyCommentsGridItem} />
-        <View style={styles.emptyCommentsGridItem} />
-        <View style={styles.emptyCommentsGridItem} />
-        <View style={[styles.emptyCommentsGridItem, styles.emptyCommentsGridItemActive]} />
-      </View>
+      <MaterialCommunityIcons name="forum-outline" size={48} color={colors.text.disabled} />
       <Text variant="caption" color={colors.text.hint} style={styles.emptyCommentsSubtitle}>
-        这里空空如也，邀请好友来互动吧！
+        评论区空空如也，来发表第一条评论吧~
       </Text>
     </View>
-  ), []);
+  ), [colors]);
 
   const openComposer = () => {
     setIsComposerVisible(true);
@@ -1382,6 +1376,7 @@ export const PostDetailScreen: React.FC = () => {
   const closeComposer = () => {
     setIsComposerVisible(false);
     setShowEmojiPanel(false);
+    setReplyingTo(null);
     Keyboard.dismiss();
   };
 
@@ -1522,6 +1517,16 @@ export const PostDetailScreen: React.FC = () => {
           {/* Toolbar */}
           <View style={styles.expandedToolbar}>
             <View style={styles.expandedToolbarLeft}>
+              <TouchableOpacity
+                style={styles.expandedToolbarItem}
+                onPress={closeComposer}
+              >
+                <MaterialCommunityIcons
+                  name="chevron-down"
+                  size={22}
+                  color={colors.text.secondary}
+                />
+              </TouchableOpacity>
               <TouchableOpacity
                 style={styles.expandedToolbarItem}
                 onPress={handlePickCommentImage}
@@ -2294,30 +2299,14 @@ function createPostDetailStyles(colors: AppColors) {
     paddingVertical: spacing.xs,
     borderRadius: borderRadius.md,
   },
-  // 空评论状态样式（类似图片中的四个方块样式）
+  // 空评论状态样式
   emptyCommentsContainer: {
     alignItems: 'center',
     justifyContent: 'center',
     paddingVertical: spacing.xl * 2.5,
   },
-  emptyCommentsGrid: {
-    flexDirection: 'row',
-    flexWrap: 'wrap',
-    width: 48,
-    height: 48,
-    marginBottom: spacing.md,
-  },
-  emptyCommentsGridItem: {
-    width: 20,
-    height: 20,
-    backgroundColor: colors.background.disabled,
-    margin: 2,
-    borderRadius: borderRadius.sm,
-  },
-  emptyCommentsGridItemActive: {
-    backgroundColor: colors.text.hint,
-  },
   emptyCommentsSubtitle: {
+    marginTop: spacing.md,
     fontSize: fontSizes.sm,
     textAlign: 'center',
     color: colors.text.hint,