feat(ui): improve navigation, component props, and chat logic

- update `app.json` with splash screen configuration
- implement tab navigation redirection in `TabsLayout` for apps and profile tabs
- update `HighlightText` prop usage from `style` to `highlightStyle` in `PostCard` and `PostContentRenderer`
- fix chat message segment construction to avoid empty text segments when sending only images
- refine UI styling by removing unnecessary shadows and adjusting `UserScreen` header visibility
- improve `HomeScreen` scroll behavior by disabling animation on FlashList scroll-to-top

src/screens/message/components/ChatScreen/styles.ts

@@ -208,11 +208,6 @@ export function createChatScreenStyles(colors: AppColors, dynamicStyles?: {
     backgroundColor: 'rgba(255, 255, 255, 0.96)',
     borderWidth: StyleSheet.hairlineWidth,
     borderColor: 'rgba(0, 0, 0, 0.08)',
-    shadowColor: colors.chat.shadow,
-    shadowOffset: { width: 0, height: 2 },
-    shadowOpacity: 0.12,
-    shadowRadius: 6,
-    elevation: 4,
   },
   jumpToLatestFabText: {
     fontSize: 13,

src/screens/message/components/ChatScreen/useChatScreen.ts

@@ -1104,7 +1104,10 @@ export const useChatScreen = (props?: ChatScreenProps) => {
     setSending(true);
 
     try {
-      const segments: MessageSegment[] = [...buildTextSegments(trimmedText, replyingTo)];
+      // 有文本或回复时才构建文本段，纯图片时不塞空 text
+      const segments: MessageSegment[] = (trimmedText || replyingTo)
+        ? [...buildTextSegments(trimmedText, replyingTo)]
+        : [];
       for (const url of uploadedUrls) {
         segments.push({
           type: 'image',