feat(frontend): wire Next.js app to backend auth, puzzles, and dashboard

[Kaylahray]

Closes #665

Summary

• Shared API client now uses NEXT_PUBLIC_API_URL and the accessToken key the auth flow actually writes.
• Email sign-in/sign-up, Google ID-token auth, and guest session call the Nest endpoints (/auth/signIn, /auth/register, /auth/google-authentication, /auth/guest-session).
• Puzzle list/detail match the backend { question, options, data/meta } shape; solve flow refreshes streak/XP after a submitted answer.
• Dashboard stats are composed from /streaks, /auth/me, and /daily-quest/status (there is no /dashboard/stats).
• Frontend next dev runs on 3001 so it does not clash with the backend on 3000.
• npm run build in frontend is green.

Notes

• Guest sessions can browse puzzles but cannot submit answers for XP (backend challenge attempts require JWT).
• Google needs NEXT_PUBLIC_GOOGLE_CLIENT_ID in frontend/.env.local.
• frontend/.env* is gitignored; locally set NEXT_PUBLIC_API_URL=http://localhost:3000.

Test plan

• npm --workspace frontend run build succeeds
• npm --workspace frontend run dev serves the app at http://localhost:3001 with backend on http://localhost:3000
• Email sign-in stores tokens and session restore hits /auth/me
• Guest session can browse puzzles
• Signed-in user: browse puzzle → submit answer → XP/streak update on the solve screen
• Dashboard shows streak / points / daily quest progress
• Landing and /auth/* do not show the Chrome sidenav

[vercel]

@Kaylahray is attempting to deploy a commit to the aminubabafatima8-gmailcom's projects Team on Vercel.

A member of the Team first needs to authorize it.

[A6dulmalik]

LGTM