Allow image uploads up to 11 MB through nginx

nginx defaults to 1 MB, so pasted screenshots failed with 413 and the order
was created without its image.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

nginx.conf

@@ -11,6 +11,8 @@ server {
     server_name _;
 
     location /api/ {
+        # Image uploads are limited to 10 MB by the frontend; nginx defaults to 1 MB.
+        client_max_body_size 11m;
         proxy_pass http://backend/api/;
         proxy_http_version 1.1;
         proxy_set_header Upgrade $http_upgrade;