Add Language detection and additional language support

[camrun91]

This puts into place the initial localized strings.

Greptile Summary

This PR introduces browser language detection and adds French and Spanish locale bundles to the YouVersion platform SDK, wiring up i18next to auto-select a locale on mount via syncBrowserLanguageFromNavigator.

• Language detection (detectLanguage.ts) reads navigator.languages/navigator.language, resolves to a supported locale via exact-then-base BCP 47 matching, and is fully SSR-guarded.
• i18n module (index.ts) adds fr and es resource bundles, calls getInitialLanguage() at module load for CSR paths, and exports syncBrowserLanguageFromNavigator as the runtime correction hook.
• YouVersionProvider calls syncBrowserLanguageFromNavigator in a useEffect([]) on mount (already updated from a previous review to avoid the SSR useLayoutEffect warning).

Confidence Score: 5/5

The change is safe to merge — detection logic is SSR-guarded, locale bundles are complete, and the two-phase init + effect approach is correct.

The detection and resolution logic is well-structured with proper SSR guards and fallback handling. Bundled resources mean init completes before the effect fires, and the idempotent check in syncBrowserLanguageFromNavigator prevents unnecessary language changes.

No files require special attention.

Important Files Changed

Filename	Overview
packages/ui/src/i18n/detectLanguage.ts	New utility: SSR-safe browser language reading and BCP 47 resolution with exact-then-base fallback. Logic is clean and well-tested.
packages/ui/src/i18n/index.ts	Adds fr/es bundles, getInitialLanguage() at module load, and syncBrowserLanguageFromNavigator export; changeLanguage errors are silently discarded via void.
packages/ui/src/components/YouVersionProvider.tsx	Adds useEffect([]) to call syncBrowserLanguageFromNavigator on mount; straightforward and SSR-safe.
packages/ui/src/i18n/index.test.ts	Comprehensive tests covering resolveBrowserLanguage, getBrowserLanguages, and full i18n instance initialisation per-language; uses vi.resetModules() correctly for isolation.
packages/ui/src/i18n/locales/es.json	New Spanish locale; all 56 keys present, matching en.json structure.
packages/ui/src/i18n/locales/fr.json	New French locale; all 56 keys present, matching en.json structure.

Sequence Diagram

sequenceDiagram
    participant Browser
    participant Module as i18n/index.ts (module load)
    participant Detect as detectLanguage.ts
    participant i18next
    participant Provider as YouVersionProvider
    participant Effect as useEffect([])

    Browser->>Module: "import @/i18n"
    Module->>Detect: "getInitialLanguage() -> getBrowserLanguages()"
    Detect-->>Module: navigator.languages (or undefined in SSR)
    Module->>Detect: resolveBrowserLanguage(langs, supportedLngs, 'en')
    Detect-->>Module: resolved locale (e.g. 'fr')
    Module->>i18next: ".init({ lng: 'fr', resources, supportedLngs, fallbackLng })"
    i18next-->>Module: initialized (async, resources are inline)

    Browser->>Provider: mount YouVersionProvider
    Provider->>Effect: schedule useEffect
    Effect->>Detect: "syncBrowserLanguageFromNavigator() -> getBrowserLanguages()"
    Detect-->>Effect: navigator.languages
    Effect->>Detect: resolveBrowserLanguage(...)
    Detect-->>Effect: resolved locale
    Effect->>i18next: "changeLanguage(locale) if i18n.language != locale"

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Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
packages/ui/src/i18n/index.ts:31
`void i18n.changeLanguage(detected)` silently swallows any rejection. With bundled resources this is unlikely to fail, but if init is still in progress or i18next is in a bad state the language will silently remain wrong with no diagnostic. A minimal `.catch` keeps the code non-blocking while at least surfacing the failure in dev.

```suggestion
    i18n.changeLanguage(detected).catch((err: unknown) => {
      console.error('[youversion-sdk] Failed to change language:', err);
    });
```

_{Reviews (3): Last reviewed commit: "Merge branch 'main' into localization" | Re-trigger Greptile}

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Latest commit: 0ddd088

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[cameronapak]

I like this PR. Good work. I am waiting on one response from Greptile

[camrun91]

@cameronapak I got the greptile things addressed