layout: fix grouping modal not shown on Linux (#1930)

apps/readest-app/src/components/ModalPortal.tsx

@@ -11,7 +11,7 @@ const ModalPortal: React.FC<ModalPortalProps> = ({ children, showOverlay = true
   return ReactDOM.createPortal(
     <div
       className={clsx(
-        'fixed inset-0 isolate z-50 flex items-center justify-center',
+        'fixed inset-0 isolate z-[100] flex items-center justify-center',
         showOverlay && 'bg-black bg-opacity-50',
       )}
       style={{ transform: 'translateZ(0)' }}

apps/readest-app/src/styles/globals.css

@@ -100,13 +100,13 @@ foliate-view {
 
 .window-border {
   border-radius: 10px;
-  z-index: 999;
+  z-index: 99;
   position: relative;
 }
 
 .window-border::before {
   content: '';
-  z-index: 1000;
+  z-index: 999;
   position: absolute;
   top: 0;
   left: 0;