PRAMOD-0007/IMVID-encryption-and-decryption ? reverse-engineered prompt

Build me a simple web app called CipherMedia that lets people upload a media file, enter a password, and either encrypt or decrypt it right in the browser.

I want it to feel clean and modern, with a dark cybersecurity style, and it should work for common media files like images, audio, and video. The main flow should be very easy, choose encrypt or decrypt, upload a file, type a password, click a button, and then download the result. Please make sure it handles basic mistakes nicely too, like missing files, empty passwords, wrong passwords, or invalid uploads, with clear messages instead of crashing.

Use Python on the backend with a Flask style setup, and build the front end with simple HTML, CSS, and JavaScript. If you need to check current library docs or best practices while building it, go ahead and look them up online.