usama-ashraf-code/SnapCaption-App ? reverse-engineered prompt

Build me a full stack social media app where people can sign up, log in, and then create image posts with captions.

I want users to be able to upload a photo from their device, see a preview before posting, add a short caption, and submit it securely. The app should keep the posting features protected so only logged in users can use them. Make the interface clean, simple, and responsive so it looks good on both desktop and mobile.

Please set up the frontend and backend so they talk to each other properly, save user and post data in a database, and handle image uploads smoothly. Use friendly error messages and success alerts so users know what is happening. If you need to check current docs or best practices online, go ahead and do that.

Please make it feel like a real polished app, not just a demo.