Update scheduled posts calendar to automatically display new posts

Invalidates the '/api/scheduled-posts' query cache on successful post creation to trigger a refetch and update the UI, resolving the need for manual page reloads.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: ae4037a0-2a6f-4530-9bac-79b543286bda
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/397bca8c-984f-43ff-841a-10897aeb8140/ae4037a0-2a6f-4530-9bac-79b543286bda/Z1TMYri

client/src/pages/new-post.tsx

@@ -213,7 +213,8 @@ export default function NewPost() {
   const createPostMutation = useMutation({
     mutationFn: (data: any) => 
       apiRequest('POST', '/api/posts', data),
-    onSuccess: () => {
+    onSuccess: async () => {
+      await queryClient.invalidateQueries({ queryKey: ['/api/scheduled-posts'], refetchType: 'all' });
       toast({
         title: "Publication créée",
         description: "La publication a été créée avec succès",