daksh7011/nyx ? reverse-engineered prompt

Build me a Kotlin multiplatform app called Nyx that lets people hide a secret text message inside an image with a password.

I want a simple flow where someone picks or takes a cover image, types their message and password, and the app turns it into a PNG that looks normal but contains the encrypted secret. Then they can save it to a private vault, share it, and later open any image, enter the password, and recover the exact message. If the password is wrong or the image has no hidden message, the app should say so clearly.

Please make it work nicely on Android, desktop, web, and iOS where possible, with a clean modern UI, light and dark themes, and a vault screen for viewing, exporting, archiving, and deleting saved images. Keep it fully offline, no account, no ads, and make sure the secret is actually encrypted before it is hidden. If you need to check current docs for the multiplatform pieces, go ahead and look them up online.