feat(i18n): add Spanish (es) locale

[kmikodev]

What

Adds Spanish (es) as a UI display language, extending the existing i18next setup that already ships English, Japanese, Simplified Chinese and Traditional Chinese.

Why

Spanish was missing from the UI locales (it previously existed only as a TTS output language). UI i18n / general localization is listed as a Tier-2 roadmap item in docs/PROJECT_STATUS.md (#411, #392, #261), so this is an additive, on-roadmap change that follows the established 4-locale pattern.

Changes

• app/src/i18n/locales/es/translation.json — new locale, 832 strings across all 18 namespaces, translated from the en master. Keys, {{interpolation}} placeholders, <code>/<path>/<link>/<strong> tags and _one/_other plural forms are preserved. Brand/model names (Whisper, Qwen3, Chatterbox, CUDA, MCP, etc.) are intentionally left untranslated.
• app/src/i18n/index.ts — register es in SUPPORTED_LANGUAGES and resources. The language switcher and the LanguageCode type derive automatically.
• app/src/lib/utils/format.ts — wire the date-fns es locale for relative-date formatting.

Verification

• Key parity vs en: 832/832 — no missing/extra keys; all {{…}} placeholders and <…> tags intact.
• biome check clean (JSON: no trailing commas, lineWidth 100).
• tsc --noEmit passes for both app and web.
• bun run build:web succeeds.

Notes

• No new dependencies (date-fns already present).
• CHANGELOG.md left untouched — it's auto-compiled during the release workflow per the file header.
• Happy to add a screenshot of the language selector or a translated screen if useful.

Summary by CodeRabbit

• New Features
  • Added Spanish language support across the app UI.
  • Users can now select Español in language settings.
  • Date-distance formatting now follows Spanish locale conventions when Spanish is selected.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ab656403-c81e-490c-9afc-f44e3acaea2b

📥 Commits

Reviewing files that changed from the base of the PR and between 559f44a and 29ebad6.

📒 Files selected for processing (1)

• app/src/i18n/index.ts

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📝 Walkthrough

Walkthrough

Spanish is added as a supported language, a complete Spanish translation catalog is registered, and date formatting now uses the Spanish locale when the active language is es.

Changes

Spanish locale support

Layer / File(s)	Summary
Spanish translation catalog app/src/i18n/locales/es/translation.json	Adds Spanish strings for navigation, captures, voices, effects, stories, generation, settings, and models workflows.
Spanish locale wiring app/src/i18n/index.ts, app/src/lib/utils/format.ts	Adds es to supported languages and i18n resources, and maps the active Spanish language to the date-fns Spanish locale.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• jamiepine/voicebox#919: Registers Spanish through the same i18n configuration.
• jamiepine/voicebox#802: Adds another language through the same i18n and date-fns locale wiring.
• jamiepine/voicebox#810: Adds another translation bundle and supported language through the same i18n setup.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding Spanish (es) locale support to i18n.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[kmikodev]

Hi @jamiepine 👋 Thanks for merging the French and pt-BR locales! This PR adds Spanish (es) following the exact same pattern.

I've rebased it on the latest main (after #802/#810 landed), so it's conflict-free, and it's green locally — typecheck for both app and web, plus build:web — with full key parity against en (850/850 keys, placeholders intact).

Whenever you get a chance, could you approve the workflow run so CI can verify it? Happy to tweak anything. 🙏