Error 400: redirect_uri_mismatch You can't sign in to this app because it doesn't comply with Google's OAuth 2.0 policy. If you're the app developer, register the redirect URI in the Google Cloud Console.
redirectに入れるってのはわかるけどどう辿るんだよ???
ここみたらそこか。
さらにここもみた zenn.dev
if (process.env.FIREBASE_CONFIG && typeof window !== 'undefined' && !firebase.apps.length) { firebase.initializeApp(JSON.parse(process.env.FIREBASE_CONFIG)) } else { console.warn('FIREBASE_CONFIG が未設定です') }