Since this is a file that you the developer own i would recommend using a service account
If you share the file with the service account it will then have permissions to access it without you needing to go though the oauth2 steps of authorizing your application.
On google cloud console simply create Service account credentials
const {google} = require('googleapis');
const auth = new google.auth.GoogleAuth({
keyFile: '/path/to/your-secret-key.json',
scopes: ['https://www.googleapis.com/auth/spreadsheets'],
});
Then change your auth code slightly. Open the service account key file and look for the service account email address its the only one witha @ in it. Share the file with the service account like you would any other user in google drive web app.
Once it has access you shouldn't need to authorize the app again.
I have a video on Google drive API upload file with Nodejs + service account which might help you a bit you just need the authorization code. Everything else you have should work as is.