Full Stack Developer - web app for semi-automated file downloading

We need a tool that:
- provides a REST API that receives a URL of a to-be-downloaded file, and then returns the downloaded file if it has been previously downloaded
- provides a web page that shows a list of all URLs that should be downloaded manually, as well as, next to each URL, a field for storing the downloaded file
- builds a database of all ULR-file pairs, so that when a file that was previously downloaded is requested again, it is provided immediately

The background of this project is that we are using automated tools to download files from web pages, however, we are now being blocked out. Since manual downloads work, we need the above tool to allow workers to manually download the files and automatically feed them into our system.

You should use C# or Python (since these are the programming languages that our programmers are using). If we are satisfied with your work on this, we would probably regularly involve you in similar future projects.

In your application, please indicate how many hours you would need to provide the above tool.