MVP SprintFirebase + Next.js

// Firebase + Next.js — smallest working version
import { initializeApp } from 'firebase/app'
import { getAuth, onAuthStateChanged, signInWithPopup, GoogleAuthProvider } from 'firebase/auth'
import { getFirestore, collection, addDoc } from 'firebase/firestore'

const app = initializeApp({/* envs */})
const auth = getAuth(app)
const db = getFirestore(app)

onAuthStateChanged(auth, async (user) => {
  if (user) await addDoc(collection(db, 'ideas'), { owner: user.uid, at: Date.now() })
})

// Google sign‑in
auth.currentUser || signInWithPopup(auth, new GoogleAuthProvider())