fix: remove stale Next.js references and update stack docs

[collinsezedike]

Description

Removes all stale Next.js references introduced during the initial scaffold, before the frontend was migrated to Vite + React in PR #3. Also corrects other outdated references found across docs and config.

Related Issue

N/A — housekeeping follow-up to PR #3 (Vite migration).

Type of Change

• fix — bug fix

Context (DeFi / Stellar)

Field	Value
Network tested on	N/A
Protocol affected	None
Touches contracts?	No
Wallet used	N/A

Changes

• README.md — Next.js 14 → Vite + React 18 in architecture block, data flow diagram, and tech stack table; fixed clone URL (your-org → collinsezedike); corrected label name to good first issue + Stellar Wave
• turbo.json — removed .next/** and !.next/cache/** from build outputs (Vite outputs to dist/ only)
• docs/github-issues.md — Issue [Trivial] Mobile-responsive layout pass #1: pages/index.tsx → App.tsx; Issue [Frontend] Add French and English i18n with locale detection #10: next-intl → react-i18next with correct packages and useTranslation() hook
• scripts/setup-github.sh — frontend label description: Vite/Next.js pages → Vite components

Checklist

• My branch follows the naming convention: chore/community-health
• My commit messages follow Conventional Commits
• No code changes — documentation and config only
• I have not committed .env files, secrets, or private keys