feat(Theme): enhance theming and UI consistency across components

- Updated app.json to set userInterfaceStyle to automatic for improved theme adaptability.
- Refactored layout components to utilize useAppColors for dynamic theming, ensuring consistent color usage.
- Introduced SystemChrome component to manage system UI background color based on theme.
- Enhanced TabsLayout, ProfileStackLayout, and other components to leverage new theming structure.
- Improved QRCodeScanner, SearchBar, and CommentItem styles to align with the updated theme system.
- Consolidated styles in SystemMessageItem and TabBar for better maintainability and visual coherence.

src/services/alertOverride.ts

@@ -39,7 +39,9 @@ export const installAlertOverride = () => {
       return;
     }
 
-    if (actionButtons.length <= 3) {
+    // 自定义对话框支持多按钮（含「主题模式」等 4 项）；Web 上原生 Alert 常不可用
+    const MAX_CUSTOM_DIALOG_ACTIONS = 8;
+    if (actionButtons.length <= MAX_CUSTOM_DIALOG_ACTIONS) {
       showDialog({
         title: nextTitle,
         message: nextMessage,
@@ -49,7 +51,6 @@ export const installAlertOverride = () => {
       return;
     }
 
-    // 极少数复杂按钮场景，保底回退原生 Alert
     nativeAlert(nextTitle, nextMessage, buttons, options);
   };
 };