Set correct API for production

On the server, requests to /api will be mapped to port 8888, where the backend container is listening

client/src/config.js

@@ -3,7 +3,7 @@ const ENV = {
 };
 
 const MIMIR_API = {
-  URL: ENV.IS_PRODUCTION ? 'http://mimir.si.usi.ch' : 'http://localhost:8888',
+  URL: ENV.IS_PRODUCTION ? 'http://mimir.si.usi.ch/api' : 'http://localhost:8888',
 };
 
 const UI = {