fix(nginx): correct proxyPass port conversion to string

Convert the port value to a string in nginx configuration to ensure correct proxyPass functionality. This change prevents potential runtime errors when using numeric port values directly in the proxyPass directive.

systems/x86_64-linux/sgx/nginx.nix

@@ -21,7 +21,7 @@
         useACMEHost = "internal.hoyer.world";
         forceSSL = true;
         locations."/" = {
-          proxyPass = "http://127.0.0.1:${config.services.open-webui.port}";
+          proxyPass = "http://127.0.0.1:${toString config.services.open-webui.port}";
         };
       };
     };