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}