Mehak024/post-composer ? reverse-engineered prompt

Build me a modern social media post composer as a small full stack web app. I want a clean responsive interface where someone can enter a title and description, optionally upload an image or video with preview, choose a platform, pick a date and time to schedule the post, and see a live character count as they type.

Make it validate the post in real time, so required fields are enforced, the scheduled time cannot be in the past, and the description respects each platform’s limit, like X at 280, Threads and Pinterest at 500, Instagram at 2200, Quora at 3000, and Facebook at 63206. If something is invalid, publishing should stay disabled.

Please include save draft and restore draft using local storage, toast style feedback messages, dark mode, and a simple backend endpoint that simulates publishing successfully. I want it to feel polished and easy to use, not just functional. React on the frontend and Node with Express on the backend is fine. Look up current docs online if you need to.