set increased timeout on api

Default timeout needs to be increased on API endpoint as well as on the websocket (though smaller) - otherwise, especially on slower systems and with large Gcode files plus object exclusion, sending directly from slicer times out with HTTP 504

resources/mainsail

@@ -55,6 +55,7 @@ server {
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Scheme $scheme;
+        proxy_read_timeout 600;
     }
 
     location /webcam/ {