Deployment & Client's upload

I wonder how the panel works after hosting and uploading on the actual website.
After the development, I checked the web includes only changed TEXTS from the panel, not images.
I can see if we want to upload some contents with new files, the person who has all code files should upload the file called “contents” to hosting server.
But what if the clients want to upload all by themselves?
Should the developer give all original codes to client or set up the deployment for site.?
I am curious if there is any way to be able to deal these issue inside of Kirby or using plugin.
If there are not, hope someone can share their easier ways to upload new contents to the server immediately on clients’ shoes!
Then I will wait for your answers.
Thank you:)