The react components must be built in order to be served by the server. To build, you must use the command npm run build.
The server will serve files in the build directory (which is populated with the npm run build command) and the files in the photos/albums directory.
To run the server use must use the command npm run start.
During the development, you should edit the baseURL in the src/settings.js file (setting it to http://locahost:5000 should be sufficient) then run the server npm start et run watcher for front npm run start:front.