When you upload any image files from the Admin/Restaurant Dashboard, the files are store in /assets directory. But the react development server will only be looking for files inside the /public folder.
Hence is an exact replica of the /assets folder is present inside the /public directory as well.
So, to fix this (just in the dev environment, this is not required on live website) you will need to copy the whole assets folder and paste it to the /public folder after you create a restaurant, item, upload logo, favicons, splashscreen or any form of image that needs to be shown on the Customer/Delivery Application.