feat(i18n): auto-detect browser language with localStorage persistence (closes #29) — v2 rebase

[zqleslie]

Summary (v2 — clean rebase on latest main)

Auto-detects the user's browser language on init and persists manual language toggles in localStorage, so the app remembers the user's preference across sessions.

Replaces PR #50 which became dirty after main received new commits.

Changes

1. CreditRoot/src/i18n/index.js

• Added i18next-browser-languagedetector via .use(LanguageDetector)
• Removed hardcoded lng: 'es'
• Configured detection:
  • order: ['localStorage', 'navigator'] — reads localStorage.getItem('ms-lang') first, falls back to navigator.language
  • lookupLocalStorage: 'ms-lang'
  • convertDetectedLanguage — if browser language starts with en, use en; otherwise default to es
• fallbackLng stays es

2. CreditRoot/package.json

• Added "i18next-browser-languagedetector": "^8.2.1" to dependencies

3. CreditRoot/src/components/layout/AppHeader.jsx

• Updated toggleLang() to persist user choice: localStorage.setItem('ms-lang', next)

Acceptance Criteria (Issue #29)

• On init, read localStorage.getItem('ms-lang') first
• If absent, parse navigator.language — if starts with en, use en; else default es
• When user toggles language in navbar, write to localStorage.setItem('ms-lang', lang)
• fallbackLng stays es
• Added i18next-browser-languagedetector to dependencies

Closes #29.

Replaces #50 (v2 clean rebase after main received new commits).