Update calendar grid to use lighter gray separators

Modify the CSS classes for the calendar grid to use `gap-px` and `bg-gray-300` for the separators, and reduce padding to `p-px`.

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/IQMY27o

client/src/components/CalendarGrid.tsx

@@ -389,7 +389,7 @@ export default function CalendarGrid({
       </div>
 
       {/* Calendar Days - Grid moderne sans arrondi */}
-      <div className="grid grid-cols-7 gap-0.5 bg-gray-500 p-0.5">
+      <div className="grid grid-cols-7 gap-px bg-gray-300 p-px">
         {paddedDays.map((date, index) => {
           const isCurrentMonth = isSameMonth(date, currentDate);
           const isTodayDate = isToday(date);