Update post scheduling to correctly handle date conversions

Correctly parse the `scheduledFor` date string into a Date object to resolve a Zod validation error when creating posts.

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/sjuGm8z

server/routes.ts

@@ -445,6 +445,11 @@ export async function registerRoutes(app: Express): Promise<Server> {
       const userId = user.id;
       const { pageIds, postType, mediaId, ...postFields } = req.body;
       
+      // Convert scheduledFor string to Date if provided
+      if (postFields.scheduledFor && typeof postFields.scheduledFor === 'string') {
+        postFields.scheduledFor = new Date(postFields.scheduledFor);
+      }
+      
       // Create the post
       const postData = insertPostSchema.parse({ ...postFields, userId });
       const post = await storage.createPost(postData);