Improve handling of client disconnection

[LilianBoulard]

I often get this kind of error logs on main:

Error: Request aborted
  at onaborted (/app/node_modules/express/lib/response.js:1052:15)
  at Immediate.<anonymous> (/app/node_modules/express/lib/response.js:1094:9)
  at processImmediate (node:internal/timers:483:21) {
    code: 'ECONNABORTED'
  }
  Error: Cannot set headers after they are sent to the client
  at ServerResponse.setHeader (node:_http_outgoing:655:11)
  at ServerResponse.header (/app/node_modules/express/lib/response.js:794:10)
  at ServerResponse.react (/build/server/middlewares/reactMiddleware.tsx:64:9)
  at /build/server/app.ts:50:20
  at Layer.handle_error (/app/node_modules/express/lib/router/layer.js:71:5)
  at trim_prefix (/app/node_modules/express/lib/router/index.js:326:13)
  at /app/node_modules/express/lib/router/index.js:286:9
  at Function.process_params (/app/node_modules/express/lib/router/index.js:346:12)
  at next (/app/node_modules/express/lib/router/index.js:280:10)
  at Layer.handle_error (/app/node_modules/express/lib/router/layer.js:67:12)

This PR fixes that by better handling ECONNABORTED and already-sent requests headers.

I've tested it for about an hour and didn't see those kind of logs anymore.