Improve calendar weekend styling for better visual clarity

Apply custom CSS classes and inline styles to the Calendar component to ensure weekend days are consistently styled with a light gray background, addressing an issue where weekend backgrounds were not rendering correctly.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: cc2d271b-82f0-4d6a-9302-a0b067ffb429
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/1957c339-2757-4d1f-8e92-e9f71a1ce58e/cc2d271b-82f0-4d6a-9302-a0b067ffb429/AvJXlQr

client/src/components/ui/calendar.tsx

@@ -28,9 +28,13 @@ function Calendar({
         ...props.modifiers,
       }}
       modifiersClassNames={{
-        weekend: "bg-gray-100 dark:bg-gray-800",
+        weekend: "weekend-day",
         ...props.modifiersClassNames,
       }}
+      modifiersStyles={{
+        weekend: { backgroundColor: '#f3f4f6' },
+        ...props.modifiersStyles,
+      }}
       classNames={{
         months: "flex flex-col sm:flex-row space-y-4 sm:space-x-4 sm:space-y-0",
         month: "space-y-4",