Fix modal overlap issue for comments displayed in the calendar

Ensure comment details are visible and not hidden behind the main modal.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: dc17873f-d870-4f45-9108-207794b849f7
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/1957c339-2757-4d1f-8e92-e9f71a1ce58e/dc17873f-d870-4f45-9108-207794b849f7/Wa8YSgr

client/src/components/CalendarGrid.tsx

@@ -12,7 +12,7 @@ function CommentModal({ isOpen, onClose, comment }: { isOpen: boolean, onClose:
 
   return (
     <Dialog open={isOpen} onOpenChange={onClose}>
-      <DialogContent className="max-w-md w-full">
+      <DialogContent className="max-w-md w-full fixed z-[99999]" style={{zIndex: 99999}}>
         <DialogHeader>
           <DialogTitle className="flex items-center gap-2">
             <MessageSquare className="w-4 h-4 text-blue-600" />